The University of Surrey has a statue of Turing on their main piazza and one of the buildings of Faculty of Engineering and Physical Sciences is named after him.
Istanbul Bilgi University organises an annual conference on the theory of computation called "Turing Days".
In the early 1960s, Stanford University named the sole lecture room of the Polya Hall Mathematics building "Alan Turing Auditorium".
One of the amphitheatres of the Computer Science department (LIFL) at the University of Lille in northern France is named in honour of Alan M. Turing (the other amphitheatre is named after Kurt Gödel).
Alan Turing Road in the Surrey Research Park and the Alan Turing Way, part of the Manchester inner ring road. Alan Turing road in Loughborough are named after Turing.
Carnegie Mellon University
has a granite bench, situated in the Hornbostel Mall, with the name
"A.M. Turing" carved across the top, "Read" down the left leg, and
"Write" down the other.
The University of Oregon has a bust of Turing on the side of Deschutes Hall, the computer science building.
Ghent University named a computer room after Turing, in their department of Computer Science and Applied Mathematics.
Nvidia unveiled their line of GeForce Graphics Cards based on the Turing microarchitecture,
which in turn was named after Turing. The architecture introduces the
first consumer products capable of real-time raytracing, which has been a
longstanding goal of the computer graphics industry.
Redmond, Washington, the location of Microsoft Corporation's
headquarters, named a street adjacent to the Microsoft main Campus
after Turing, along with streets named for other historically
significant scientists and inventors.
The University of Wolverhampton has a tribunal "Alan Turing" building in honour of the code breaker.
A biography published by the Royal Society shortly after Turing's death, while his wartime work was still subject to the Official Secrets Act, recorded:
Three remarkable papers written
just before the war, on three diverse mathematical subjects, show the
quality of the work that might have been produced if he had settled down
to work on some big problem at that critical time. For his work at the
Foreign Office he was awarded the OBE.
Since 1966, the Turing Award has been given annually by the Association for Computing Machinery
for technical or theoretical contributions to the computing community.
It is widely considered to be the computing world's highest honour,
equivalent to the Nobel Prize.
On 23 June 1998, on what would have been Turing's 86th birthday, his biographer, Andrew Hodges, unveiled an official English Heritageblue plaque at his birthplace in Warrington Crescent, London, later the Colonnade Hotel.
To mark the 50th anniversary of his death, a memorial plaque was
unveiled on 7 June 2004 at his former residence, Hollymeade, in Wilmslow, Cheshire.
On 13 March 2000, Saint Vincent and the Grenadines
issued a set of postage stamps to celebrate the greatest achievements
of the 20th century, one of which carries a portrait of Turing against a
background of repeated 0s and 1s and is captioned: "1937: Alan Turing's
theory of digital computing". On 1 April 2003, Turing's work at Bletchley Park was named an IEEE Milestone. On 28 October 2004, a bronze statue of Turing sculpted by John W. Mills was unveiled at the University of Surrey in Guildford, marking the 50th anniversary of Turing's death; it portrays him carrying his books across the campus.
Turing was one of four mathematicians examined in the BBC documentary entitled Dangerous Knowledge (2008). The Princeton Alumni Weekly named Turing the second most significant alumnus in the history of Princeton University, second only to President James Madison.
A 1.5-ton, life-size statue of Turing was unveiled on 19 June 2007 at
Bletchley Park. Built from approximately half a million pieces of Welsh slate, it was sculpted by Stephen Kettle, having been commissioned by the American billionaire Sidney Frank.
Turing memorial statue plaque in Sackville Park, Manchester
Turing has been honoured in various ways in Manchester, the city where he worked towards the end of his life. In 1994, a stretch of the A6010 road
(the Manchester city intermediate ring road) was named "Alan Turing
Way". A bridge carrying this road was widened and carries the name Alan
Turing Bridge A statue of Turing was unveiled in Manchester on 23 June 2001 in Sackville Park, between the University of Manchester building on Whitworth Street and Canal Street.
The memorial statue depicts the "father of computer science" sitting
on a bench at a central position in the park, holding an apple. The cast
bronze bench carries in relief the text "Alan Mathison Turing
1912–1954" and "IEKYF ROMSI ADXUO KVKZC GUBJ". The latter is described
as "a motto as encoded by the German 'Enigma'".
A plaque at the statue's feet reads "Father of Computer Science,
Mathematician, Logician, Wartime Codebreaker, Victim of Prejudice",
followed by a Bertrand Russell
quotation: "Mathematics, rightly viewed, possesses not only truth but
supreme beauty, a beauty cold and austere like that of sculpture."
In 1999, Time magazine named Turing as one of the 100 Most Important People of the 20th century
and stated, "The fact remains that everyone who taps at a keyboard,
opening a spreadsheet or a word-processing program, is working on an
incarnation of a Turing machine."
In 2002, Turing was ranked twenty-first on the BBC's poll of the 100 Greatest Britons following a UK-wide vote. In 2006, British writer and mathematician Ioan James
chose Turing as one of twenty people to feature in his book about
famous historical figures who may have had some of the traits of Asperger syndrome. In 2010, actor/playwright Jade Esteban Estrada portrayed Turing in the solo musical, Icons: The Lesbian and Gay History of the World, Vol. 4. In 2011, in The Guardian's "My hero" series, writer Alan Garner
chose Turing as his hero and described how they had met while out
jogging in the early 1950s. Garner remembered Turing as "funny and
witty" and said that he "talked endlessly". In 2006, Turing was named with online resources as an LGBT History Month Icon. In 2006, Boston Pride named Turing their Honorary Grand Marshal.
The logo of Apple Inc. is often erroneously referred to as a tribute to Turing, with the bite mark a reference to his death. Both the designer of the logo and the company deny that there is any homage to Turing in the design. Stephen Fry has recounted asking Steve Jobs whether the design was intentional, saying that Jobs' response was, "God, we wish it were." In February 2011, Turing's papers from the Second World War were bought for the nation with an 11th-hour bid by the National Heritage Memorial Fund, allowing them to stay at Bletchley Park.
In 2012, Turing was inducted into the Legacy Walk, an outdoor public display that celebrates LGBT history and people.
The song "Alan et la Pomme", by francophone singer-songwriter Salvatore Adamo, is a tribute to Turing. Turing's life and work featured in a BBC children's programme about famous scientists, Absolute Genius with Dick and Dom, first broadcast on 12 March 2014.
On 17 May 2014, the world's first work of public art to recognise
Turing as gay was commissioned in Bletchley, close by to Bletchley Park
where his war-time work was carried out. The commission was announced
to mark International Day Against Homophobia, Transphobia and Biphobia.
The work was unveiled at a ceremony on Turing's birthday, 23 June 2014,
and is placed alongside busy Watling Street, the old main road to
London, where Turing himself would have passed by on many occasions. On
22 October 2014, Turing was inducted into the NSA Hall of Honor.
In July 2019, the Bank of England announced that Turing's portrait would appear on the next edition of the Bank of England £50 note, to be released in 2021. He is the first openly gay person to appear on a banknote.
In 2021, Turing's former residence, Hollymeade, on Adlington Road, Wilmslow, was offered for sale by estate agent Savills, having previously been sold in 2013.
To mark the 100th anniversary of Turing's birth, the Turing Centenary Advisory Committee (TCAC) coordinated the Alan Turing Year, a year-long programme of events around the world honouring Turing's life and achievements. The TCAC, chaired by S. Barry Cooper with Turing's nephew Sir John Dermot Turing
acting as Honorary President, worked with the University of Manchester
faculty members and a broad spectrum of people from Cambridge University
and Bletchley Park.
On 23 June 2012, Google featured an interactive doodle
where visitors had to change the instructions of a Turing Machine, so
when run, the symbols on the tape would match a provided sequence,
featuring "Google" in Baudot-Murray code.
The Bletchley Park Trust collaborated with Winning Moves to publish an Alan Turing edition of the board game Monopoly.
The game's squares and cards have been revised to tell the story of
Turing's life, from his birthplace in Maida Vale to Hut 8 at Bletchley
Park. The game also includes a replica of an original hand-drawn board created by William Newman, son of Turing's mentor, Max Newman, which Turing played on in the 1950s.
In the Philippines, the Department of Philosophy at De La Salle University-Manila
hosted Turing 2012, an international conference on philosophy,
artificial intelligence, and cognitive science from 27 to 28 March 2012
to commemorate the centenary birth of Turing. Madurai, India held celebrations with a programme attended by 6,000 students.
The London 2012Olympic Torch flame was passed on in front of Turing's statue in Manchester on his 100th birthday.
There was a three-day conference in Manchester in June, the Alan Turing Centenary Conference,
a two-day conference in San Francisco, organised by the ACM, and a
birthday party and Turing Centenary Conference in Cambridge organised at
King's College, Cambridge, and the University of Cambridge, the latter organised by the association Computability in Europe.
The Science Museum in London launched a free exhibition devoted to Turing's life and achievements in June 2012, to run until July 2013. In February 2012, the Royal Mail issued a stamp featuring Turing as part of its "Britons of Distinction" series. The London 2012Olympic Torch flame was passed on in front of Turing's statue in Sackville Gardens, Manchester, on the evening of 23 June 2012, the 100th anniversary of his birth.
On 22 June 2012, Manchester City Council, in partnership with the Lesbian and Gay Foundation,
launched the Alan Turing Memorial Award, which will recognise
individuals or groups who have made a significant contribution to the
fight against homophobia in Manchester.
Previous events have included a celebration of Turing's life and
achievements, at the University of Manchester, arranged by the British
Logic Colloquium and the British Society for the History of Mathematics on 5 June 2004.
In the shared alternate history of Ill Bethisad (1997 and after), Alan Turing was a mathematician, computer scientist, logician, etc. in much the same way as reality. Like his real-life counterpart, the fictional alternate universe version of Turing devised the Turing machine and the "Turing" version of the Church–Turing thesis. During the "Second Great War" (the equivalent of World War II), Turing worked for the British government, breaking codes produced by the German Enigma machine by a machine partially created by him called the "Bombe".
In theatre
Breaking the Code is a 1986 play by Hugh Whitemore about Turing. The play ran in London's West End beginning in November 1986 and on Broadway from 15 November 1987 to 10 April 1988. In these performances, Turing was played by Derek Jacobi. The Broadway production was nominated for three Tony Awards including Best Actor in a Play, Best Featured Actor in a Play, and Best Direction of a Play, and for two Drama Desk Awards, for Best Actor and Best Featured Actor. Turing was again portrayed by Jacobi in the 1996 television film adaptation of Breaking the Code.
In 2012, in honour of the Turing Centennial, American Lyric Theater
commissioned an operatic exploration of the life and death of Turing
from composer Justine F. Chen and librettist David Simpatico. Titled The Life and Death(s) of Alan Turing,
the opera is a historical fantasia on the life of Turing. In November
2014, the opera and several other artistic works inspired by Turing's
life were featured on Studio 360. The opera received its first public performance in January 2017. In February 2019, Chicago Opera Theater
presented the orchestra workshop, and on March 23 & 25, 2023, the
company presented the fully staged world premiere at the Harris Theater
for Music and Dance in Chicago, IL.
In literature
Turing was the subject of a clerihew written by the pupils of his alma mater, Sherborne School in England:
Turing
Must have been alluring
To get made a don
So early on.
In William Gibson's 1984 Neuromancer, the Turing police are an international agency with jurisdiction over AIs.
The 2009 novel Fall of Man in Wilmslow by David Lagercrantz
is a fictional account of the investigation of Alan Turing's death
written from the point of view of the investigating police officer.
The 2015 novel Speak, written by Louisa Hall,
includes a series of fictional letters written from Turing to his best
friend's mother throughout his life, detailing his research about
artificial intelligence.
In the graphic novel series Über, in which a fictionalised version of WWII plays out involving superhuman soldiers called "Tank-Men", Turing is one of the researchers as well as a Tank-Man himself.
Electronic music duo Matmos released an EP titled For Alan Turing in 2006, which was based on material commissioned by Dr. Robert Osserman and David Elsenbud of the Mathematical Sciences Research Institute. In one of its tracks, an original Enigma Machine is sampled.
In 2012, Spanish group Hidrogenesse dedicated their LP Un dígito binario dudoso. Recital para Alan Turing (A dubious binary digit. Concert for Alan Turing) to the memory of the mathematician.
A musical work inspired by Turing's life, written by Neil Tennant and Chris Lowe of the Pet Shop Boys, entitled A Man from the Future, was announced in late 2013. It was performed by the Pet Shop Boys and Juliet Stevenson (narrator), the BBC Singers, and the BBC Concert Orchestra conducted by Dominic Wheeler at the BBC Proms in the Royal Albert Hall on 23 July 2014.
Codebreaker is also the title of a choral work by the composer James McCarthy. It includes settings of texts by the poets Wilfred Owen, Sara Teasdale, Walt Whitman, Oscar Wilde and Robert Burns that are used to illustrate aspects of Turing's life. It was premiered on 26 April 2014 at the Barbican Centre in London, where it was performed by the Hertfordshire Chorus, who commissioned the work, led by David Temple with the soprano soloist Naomi Harvey providing the voice of Turing's mother.
Turing, a two-act opera with music by Anno Schreier and libretto by Georg Holzer. Premiere 26 November 2022 at the Nürnberg Staatstheater, conducted by Guido Johannes Rumstadt, with Martin Platz in the title role.
Codebreaker, original UK title Britain's Greatest Codebreaker, is a TV film that aired on 21 November 2011 by Channel 4
about Turing's life. It had a limited release in the US beginning on 17
October 2012. The story is told as a discussion between Turing and his
psychiatrist Dr. Franz Greenbaum. The story is based on journals
maintained by Greenbaum and others who have studied Turing's life as
well as some of his colleagues.
The historical drama film The Imitation Game, directed by Morten Tyldum and starring Benedict Cumberbatch as Turing and Keira Knightley as Joan Clarke,
was released in the UK on 14 November 2014 and released theatrically in
the US on 28 November 2014. The story, loosely based on Hodges' 1983
biography, concentrates on the period of Turing's life where he breaks
the Enigma code with other codebreakers in Bletchley Park. It received the Academy Award for Best Adapted Screenplay in 2015. It was a tremendous success, bringing in $233.6 million for a production cost of $14 million.
During the Second World War, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence. For a time he led Hut 8,
the section that was responsible for German naval cryptanalysis. Here,
he devised a number of techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bomba method, an electromechanical machine that could find settings for the Enigma machine. Turing played a crucial role in cracking intercepted coded messages that enabled the Allies to defeat the Axis powers in many crucial engagements, including the Battle of the Atlantic.
Turing was prosecuted in 1952 for homosexual acts. He accepted hormone treatment with DES, a procedure commonly referred to as chemical castration, as an alternative to prison. Turing died on 7 June 1954, at age 41, from cyanide poisoning. An inquest determined his death as a suicide, but it has been noted that the known evidence is also consistent with accidental poisoning.
Following a public campaign in 2009, British prime minister Gordon Brown made an official public apology on behalf of the government for "the appalling way [Turing] was treated". Queen Elizabeth II granted a posthumous pardon in 2013. The term "Alan Turing law"
is now used informally to refer to a 2017 law in the United Kingdom
that retroactively pardoned men cautioned or convicted under historical
legislation that outlawed homosexual acts.
Turing was born in Maida Vale, London, while his father, Julius Mathison Turing was on leave from his position with the Indian Civil Service (ICS) of the British Raj government at Chatrapur, then in the Madras Presidency and presently in Odisha state, in India.
Turing's father was the son of a clergyman, the Rev. John Robert
Turing, from a Scottish family of merchants that had been based in the
Netherlands and included a baronet. Turing's mother, Julius's wife, was Ethel Sara Turing (née Stoney), daughter of Edward Waller Stoney, chief engineer of the Madras Railways. The Stoneys were a ProtestantAnglo-Irishgentry family from both County Tipperary and County Longford, while Ethel herself had spent much of her childhood in County Clare. Julius and Ethel married on 1 October 1907 at Bartholomew's church on Clyde Road, in Dublin.
Julius's work with the ICS brought the family to British India, where his grandfather had been a general in the Bengal Army. However, both Julius and Ethel wanted their children to be brought up in Britain, so they moved to Maida Vale, London, where Alan Turing was born on 23 June 1912, as recorded by a blue plaque on the outside of the house of his birth, later the Colonnade Hotel. Turing had an elder brother, John Ferrier Turing, father of Sir John Dermot Turing, 12th Baronet of the Turing baronets.
Turing's father's civil service commission was still active during Turing's childhood years, and his parents travelled between Hastings in the United Kingdom and India, leaving their two sons to stay with a retired Army couple. At Hastings, Turing stayed at Baston Lodge, Upper Maze Hill, St Leonards-on-Sea, now marked with a blue plaque. The plaque was unveiled on 23 June 2012, the centenary of Turing's birth.
Very early in life, Turing showed signs of the genius that he was later to display prominently. His parents purchased a house in Guildford in 1927, and Turing lived there during school holidays. The location is also marked with a blue plaque.
School
Turing's parents enrolled him at St Michael's, a primary school at 20 Charles Road, St Leonards-on-Sea,
from the age of six to nine. The headmistress recognised his talent,
noting that she has "...had clever boys and hardworking boys, but Alan
is a genius".
Between January 1922 and 1926, Turing was educated at Hazelhurst Preparatory School, an independent school in the village of Frant in Sussex (now East Sussex). In 1926, at the age of 13, he went on to Sherborne School, an independent boarding school in the market town of Sherborne in Dorset, where he boarded at Westcott House. The first day of term coincided with the 1926 General Strike, in Britain, but Turing was so determined to attend that he rode his bicycle unaccompanied 60 miles (97 km) from Southampton to Sherborne, stopping overnight at an inn.
Turing's natural inclination towards mathematics and science did
not earn him respect from some of the teachers at Sherborne, whose definition of education placed more emphasis on the classics.
His headmaster wrote to his parents: "I hope he will not fall between
two stools. If he is to stay at public school, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at a public school".
Despite this, Turing continued to show remarkable ability in the
studies he loved, solving advanced problems in 1927 without having
studied even elementary calculus. In 1928, aged 16, Turing encountered Albert Einstein's work; not only did he grasp it, but it is possible that he managed to deduce Einstein's questioning of Newton's laws of motion from a text in which this was never made explicit.
Christopher Morcom
At Sherborne, Turing formed a significant friendship with fellow
pupil Christopher Collan Morcom (13 July 1911 – 13 February 1930), who has been described as Turing's first love.
Their relationship provided inspiration in Turing's future endeavours,
but it was cut short by Morcom's death, in February 1930, from
complications of bovine tuberculosis, contracted after drinking infected cow's milk some years previously.
The event caused Turing great sorrow. He coped with his grief by working
that much harder on the topics of science and mathematics that he had
shared with Morcom. In a letter to Morcom's mother, Frances Isobel
Morcom (née Swan), Turing wrote:
I
am sure I could not have found anywhere another companion so brilliant
and yet so charming and unconceited. I regarded my interest in my work,
and in such things as astronomy (to which he introduced me) as something
to be shared with him and I think he felt a little the same about
me ... I know I must put as much energy if not as much interest into my
work as if he were alive, because that is what he would like me to do.
Turing's relationship with Morcom's mother continued long after Morcom's
death, with her sending gifts to Turing, and him sending letters,
typically on Morcom's birthday. A day before the third anniversary of Morcom's death (13 February 1933), he wrote to Mrs. Morcom:
I
expect you will be thinking of Chris when this reaches you. I shall
too, and this letter is just to tell you that I shall be thinking of
Chris and of you tomorrow. I am sure that he is as happy now as he was
when he was here. Your affectionate Alan.
Some have speculated that Morcom's death was the cause of Turing's atheism and materialism.
Apparently, at this point in his life he still believed in such
concepts as a spirit, independent of the body and surviving death. In a
later letter, also written to Morcom's mother, Turing wrote:
Personally,
I believe that spirit is really eternally connected with matter but
certainly not by the same kind of body ... as regards the actual
connection between spirit and body I consider that the body can hold on
to a 'spirit', whilst the body is alive and awake the two are firmly
connected. When the body is asleep I cannot guess what happens but when
the body dies, the 'mechanism' of the body, holding the spirit is gone
and the spirit finds a new body sooner or later, perhaps immediately.
University and work on computability
After graduating from Sherborne, Turing applied for several Cambridge colleges scholarships, including Trinity and King's, eventually earning an £80 per annum scholarship (equivalent to about £4,300 as of 2023) to study at the latter. There, Turing studied the undergraduate course in Schedule B (that is, a three-year Parts I and II, of the Mathematical Tripos,
with extra courses at the end of the third year, as Part III only
emerged as a separate degree in 1934) from February 1931 to November
1934 at King's College, Cambridge, where he was awarded first-class honours in mathematics. His dissertation, On the Gaussian error function, written during his senior year and delivered in November 1934 (with a deadline date of 6 December) proved a version of the central limit theorem.
It was finally accepted on 16 March 1935. By spring of that same year,
Turing started his master's course (Part III)—which he completed in
1937—and, at the same time, he published his first paper, a one-page
article called Equivalence of left and right almost periodicity (sent on 23 April), featured in the tenth volume of the Journal of the London Mathematical Society. Later that year, Turing was elected a Fellow of King's College on the strength of his dissertation. However, and, unknown to Turing, this version of the theorem he proved in his paper, had already been proven, in 1922, by Jarl Waldemar Lindeberg.
Despite this, the committee found Turing's methods original and so
regarded the work worthy of consideration for the fellowship. Abram Besicovitch's
report for the committee went so far as to say that if Turing's work
had been published before Lindeberg's, it would have been "an important
event in the mathematical literature of that year".
Between the springs of 1935 and 1936, at the same time as Church,
Turing worked on the decidability of problems, starting from Godel's
incompleteness theorems. In mid-April 1936, Turing sent Max Newman the
first draft typescript of his investigations. That same month, Alonzo
Church published his An Unsolvable Problem of Elementary Number Theory,
with similar conclusions to Turing's then-yet unpublished work.
Finally, on 28 May of that year, he finished and delivered his 36-page
paper for publication called "On Computable Numbers, with an Application to the Entscheidungsproblem". It was published in the Proceedings of the London Mathematical Society journal in two parts, the first on 30 November and the second on 23 December. In this paper, Turing reformulated Kurt Gödel's
1931 results on the limits of proof and computation, replacing Gödel's
universal arithmetic-based formal language with the formal and simple
hypothetical devices that became known as Turing machines. The Entscheidungsproblem (decision problem) was originally posed by German mathematician David Hilbert
in 1928. Turing proved that his "universal computing machine" would be
capable of performing any conceivable mathematical computation if it
were representable as an algorithm. He went on to prove that there was no solution to the decision problem by first showing that the halting problem for Turing machines is undecidable:
it is not possible to decide algorithmically whether a Turing machine
will ever halt. This paper has been called "easily the most influential
math paper in history".
King's College, Cambridge, where Turing was an undergraduate in 1931 and became a Fellow in 1935. The computer room is named after him.
Although Turing's proof was published shortly after Alonzo Church's equivalent proof using his lambda calculus, Turing's approach is considerably more accessible and intuitive than Church's. It also included a notion of a 'Universal Machine' (now known as a universal Turing machine),
with the idea that such a machine could perform the tasks of any other
computation machine (as indeed could Church's lambda calculus).
According to the Church–Turing thesis, Turing machines and the lambda calculus are capable of computing anything that is computable. John von Neumann acknowledged that the central concept of the modern computer was due to Turing's paper. To this day, Turing machines are a central object of study in theory of computation.
From September 1936 to July 1938, Turing spent most of his time studying under Church at Princeton University, in the second year as a Jane Eliza Procter Visiting Fellow.
In addition to his purely mathematical work, he studied cryptology and
also built three of four stages of an electro-mechanical binary multiplier. In June 1938, he obtained his PhD from the Department of Mathematics at Princeton; his dissertation, Systems of Logic Based on Ordinals, introduced the concept of ordinal logic and the notion of relative computing, in which Turing machines are augmented with so-called oracles, allowing the study of problems that cannot be solved by Turing machines. John von Neumann wanted to hire him as his postdoctoral assistant, but he went back to the United Kingdom.
Career and research
When Turing returned to Cambridge, he attended lectures given in 1939 by Ludwig Wittgenstein about the foundations of mathematics. The lectures have been reconstructed verbatim, including interjections from Turing and other students, from students' notes. Turing and Wittgenstein argued and disagreed, with Turing defending formalism and Wittgenstein propounding his view that mathematics does not discover any absolute truths, but rather invents them.
Cryptanalysis
During the Second World War, Turing was a leading participant in the breaking of German ciphers at Bletchley Park. The historian and wartime codebreaker Asa Briggs has said, "You needed exceptional talent, you needed genius at Bletchley and Turing's was that genius."
From September 1938, Turing worked part-time with the Government Code and Cypher School (GC&CS), the British codebreaking organisation. He concentrated on cryptanalysis of the Enigma cipher machine used by Nazi Germany, together with Dilly Knox, a senior GC&CS codebreaker. Soon after the July 1939 meeting near Warsaw at which the Polish Cipher Bureau gave the British and French details of the wiring of Enigma machine's rotors and their method of decrypting Enigma machine's messages, Turing and Knox developed a broader solution. The Polish method relied on an insecure indicator
procedure that the Germans were likely to change, which they in fact
did in May 1940. Turing's approach was more general, using crib-based decryption for which he produced the functional specification of the bombe (an improvement on the Polish Bomba).
Two cottages in the stable yard at Bletchley Park. Turing worked here in 1939 and 1940, before moving to Hut 8.
On 4 September 1939, the day after the UK declared war on Germany,
Turing reported to Bletchley Park, the wartime station of GC&CS. Like all others who came to Bletchley, he was required to sign the Official Secrets Act, in which he agreed not to disclose anything about his work at Bletchley, with severe legal penalties for violating the Act.
Specifying the bombe was the first of five major cryptanalytical
advances that Turing made during the war. The others were: deducing the
indicator procedure used by the German navy; developing a statistical
procedure dubbed Banburismus for making much more efficient use of the bombes; developing a procedure dubbed Turingery for working out the cam settings of the wheels of the Lorenz SZ 40/42 (Tunny) cipher machine and, towards the end of the war, the development of a portable secure voice scrambler at Hanslope Park that was codenamed Delilah.
By using statistical techniques to optimise the trial of different
possibilities in the code breaking process, Turing made an innovative
contribution to the subject. He wrote two papers discussing mathematical
approaches, titled The Applications of Probability to Cryptography and Paper on Statistics of Repetitions, which were of such value to GC&CS and its successor GCHQ that they were not released to the UK National Archives
until April 2012, shortly before the centenary of his birth. A GCHQ
mathematician, "who identified himself only as Richard," said at the
time that the fact that the contents had been restricted under the
Official Secrets Act for some 70 years demonstrated their importance,
and their relevance to post-war cryptanalysis:
[He]
said the fact that the contents had been restricted "shows what a
tremendous importance it has in the foundations of our subject". ... The
papers detailed using "mathematical analysis to try and determine which
are the more likely settings so that they can be tried as quickly as
possible". ... Richard said that GCHQ had now "squeezed the juice" out
of the two papers and was "happy for them to be released into the public
domain".
Turing had a reputation for eccentricity at Bletchley Park. He was
known to his colleagues as "Prof" and his treatise on Enigma was known
as the "Prof's Book". According to historian Ronald Lewin, Jack Good, a cryptanalyst who worked with Turing, said of his colleague:
In the first week of June each year
he would get a bad attack of hay fever, and he would cycle to the
office wearing a service gas mask to keep the pollen off. His bicycle
had a fault: the chain would come off at regular intervals. Instead of
having it mended he would count the number of times the pedals went
round and would get off the bicycle in time to adjust the chain by hand.
Another of his eccentricities is that he chained his mug to the
radiator pipes to prevent it being stolen.
Peter Hilton recounted his experience working with Turing in Hut 8 in his "Reminiscences of Bletchley Park" from A Century of Mathematics in America:
It is a rare experience to meet an
authentic genius. Those of us privileged to inhabit the world of
scholarship are familiar with the intellectual stimulation furnished by
talented colleagues. We can admire the ideas they share with us and are
usually able to understand their source; we may even often believe that
we ourselves could have created such concepts and originated such
thoughts. However, the experience of sharing the intellectual life of a
genius is entirely different; one realizes that one is in the presence
of an intelligence, a sensibility of such profundity and originality
that one is filled with wonder and excitement.
Alan Turing was such a genius, and those, like myself, who had the
astonishing and unexpected opportunity, created by the strange
exigencies of the Second World War, to be able to count Turing as
colleague and friend will never forget that experience, nor can we ever
lose its immense benefit to us.
Hilton echoed similar thoughts in the Nova PBS documentary Decoding Nazi Secrets.
While working at Bletchley, Turing, who was a talented long-distance runner, occasionally ran the 40 miles (64 km) to London when he was needed for meetings, and he was capable of world-class marathon standards.
Turing tried out for the 1948 British Olympic team, but he was hampered
by an injury. His tryout time for the marathon was only 11 minutes
slower than British silver medallist Thomas Richards' Olympic race time
of 2 hours 35 minutes. He was Walton Athletic Club's best runner, a fact
discovered when he passed the group while running alone. When asked why he ran so hard in training he replied:
I have such a stressful job that
the only way I can get it out of my mind is by running hard; it's the
only way I can get some release.
Due to the problems of counterfactual history, it is hard to estimate the precise effect Ultra intelligence had on the war. However, official war historian Harry Hinsley estimated that this work shortened the war in Europe by more than two years and saved over 14 million lives.
At the end of the war, a memo was sent to all those who had
worked at Bletchley Park, reminding them that the code of silence
dictated by the Official Secrets Act did not end with the war but would
continue indefinitely. Thus, even though Turing was appointed an Officer of the Order of the British Empire (OBE) in 1946 by King George VI for his wartime services, his work remained secret for many years.
Bombe
Within weeks of arriving at Bletchley Park, Turing had specified an electromechanical machine called the bombe, which could break Enigma more effectively than the Polish bomba kryptologiczna, from which its name was derived. The bombe, with an enhancement suggested by mathematician Gordon Welchman, became one of the primary tools, and the major automated one, used to attack Enigma-enciphered messages.
The
bombe searched for possible correct settings used for an Enigma message
(i.e., rotor order, rotor settings and plugboard settings) using a
suitable crib: a fragment of probable plaintext. For each possible setting of the rotors (which had on the order of 1019 states, or 1022 states for the four-rotor U-boat variant), the bombe performed a chain of logical deductions based on the crib, implemented electromechanically.
The bombe detected when a contradiction had occurred and ruled
out that setting, moving on to the next. Most of the possible settings
would cause contradictions and be discarded, leaving only a few to be
investigated in detail. A contradiction would occur when an enciphered
letter would be turned back into the same plaintext letter, which was
impossible with the Enigma. The first bombe was installed on 18 March
1940.
By late 1941, Turing and his fellow cryptanalysts Gordon Welchman, Hugh Alexander and Stuart Milner-Barry were frustrated. Building on the work of the Poles,
they had set up a good working system for decrypting Enigma signals,
but their limited staff and bombes meant they could not translate all
the signals. In the summer, they had considerable success, and shipping
losses had fallen to under 100,000 tons a month; however, they badly
needed more resources to keep abreast of German adjustments. They had
tried to get more people and fund more bombes through the proper
channels, but had failed.
On 28 October they wrote directly to Winston Churchill
explaining their difficulties, with Turing as the first named. They
emphasised how small their need was compared with the vast expenditure
of men and money by the forces and compared with the level of assistance
they could offer to the forces. As Andrew Hodges, biographer of Turing, later wrote, "This letter had an electric effect." Churchill wrote a memo to General Ismay,
which read: "ACTION THIS DAY. Make sure they have all they want on
extreme priority and report to me that this has been done." On 18
November, the chief of the secret service reported that every possible
measure was being taken.
The cryptographers at Bletchley Park did not know of the Prime
Minister's response, but as Milner-Barry recalled, "All that we did
notice was that almost from that day the rough ways began miraculously
to be made smooth." More than two hundred bombes were in operation by the end of the war.
Statue of Turing holding an Enigma machine by Stephen Kettle at Bletchley Park, commissioned by Sidney Frank, built from half a million pieces of Welsh slate
Hut 8 and the naval Enigma
Turing decided to tackle the particularly difficult problem of cracking the German naval use of Enigma "because no one else was doing anything about it and I could have it to myself". In December 1939, Turing solved the essential part of the naval indicator system, which was more complex than the indicator systems used by the other services.
That same night, he also conceived of the idea of Banburismus, a sequential statistical technique (what Abraham Wald later called sequential analysis)
to assist in breaking the naval Enigma, "though I was not sure that it
would work in practice, and was not, in fact, sure until some days had
actually broken". For this, he invented a measure of weight of evidence that he called the ban. Banburismus could rule out certain sequences of the Enigma rotors, substantially reducing the time needed to test settings on the bombes. Later this sequential process of accumulating sufficient weight of evidence using decibans (one tenth of a ban) was used in cryptanalysis of the Lorenz cipher.
Turing travelled to the United States in November 1942 and worked
with US Navy cryptanalysts on the naval Enigma and bombe construction
in Washington. He also visited their Computing Machine Laboratory in Dayton, Ohio.
Turing's reaction to the American bombe design was far from enthusiastic:
The American Bombe programme was to
produce 336 Bombes, one for each wheel order. I used to smile inwardly
at the conception of Bombe hut routine implied by this programme, but
thought that no particular purpose would be served by pointing out that
we would not really use them in that way.
Their test (of commutators) can hardly be considered conclusive as they
were not testing for the bounce with electronic stop finding devices.
Nobody seems to be told about rods or offiziers or banburismus unless
they are really going to do something about it.
During this trip, he also assisted at Bell Labs with the development of secure speech devices. He returned to Bletchley Park in March 1943. During his absence, Hugh Alexander had officially assumed the position of head of Hut 8, although Alexander had been de facto
head for some time (Turing having little interest in the day-to-day
running of the section). Turing became a general consultant for
cryptanalysis at Bletchley Park.
Alexander wrote of Turing's contribution:
There should be no question in
anyone's mind that Turing's work was the biggest factor in Hut 8's
success. In the early days, he was the only cryptographer who thought
the problem worth tackling and not only was he primarily responsible for
the main theoretical work within the Hut, but he also shared with
Welchman and Keen the chief credit for the invention of the bombe. It is
always difficult to say that anyone is 'absolutely indispensable', but
if anyone was indispensable to Hut 8, it was Turing. The pioneer's work
always tends to be forgotten when experience and routine later make
everything seem easy and many of us in Hut 8 felt that the magnitude of
Turing's contribution was never fully realised by the outside world.
Turingery
In July 1942, Turing devised a technique termed Turingery (or jokingly Turingismus) for use against the Lorenz cipher messages produced by the Germans' new Geheimschreiber (secret writer) machine. This was a teleprinterrotor cipher attachment codenamed Tunny at Bletchley Park. Turingery was a method of wheel-breaking, i.e., a procedure for working out the cam settings of Tunny's wheels. He also introduced the Tunny team to Tommy Flowers who, under the guidance of Max Newman, went on to build the Colossus computer, the world's first programmable digital electronic computer, which replaced a simpler prior machine (the Heath Robinson), and whose superior speed allowed the statistical decryption techniques to be applied usefully to the messages.
Some have mistakenly said that Turing was a key figure in the design of
the Colossus computer. Turingery and the statistical approach of
Banburismus undoubtedly fed into the thinking about cryptanalysis of the Lorenz cipher, but he was not directly involved in the Colossus development.
Delilah
Following his work at Bell Labs in the US,
Turing pursued the idea of electronic enciphering of speech in the
telephone system. In the latter part of the war, he moved to work for
the Secret Service's Radio Security Service (later HMGCC) at Hanslope Park. At the park, he further developed his knowledge of electronics with the assistance of REME officer Donald Bayley. Together they undertook the design and construction of a portable secure voice communications machine codenamed Delilah.
The machine was intended for different applications, but it lacked the
capability for use with long-distance radio transmissions. In any case,
Delilah was completed too late to be used during the war. Though the
system worked fully, with Turing demonstrating it to officials by
encrypting and decrypting a recording of a Winston Churchill speech, Delilah was not adopted for use. Turing also consulted with Bell Labs on the development of SIGSALY, a secure voice system that was used in the later years of the war.
Between 1945 and 1947, Turing lived in Hampton, London, while he worked on the design of the ACE (Automatic Computing Engine) at the National Physical Laboratory (NPL). He presented a paper on 19 February 1946, which was the first detailed design of a stored-program computer. Von Neumann's incomplete First Draft of a Report on the EDVAC had predated Turing's paper, but it was much less detailed and, according to John R. Womersley, Superintendent of the NPL Mathematics Division, it "contains a number of ideas which are Dr. Turing's own".
Although ACE was a feasible design, the effect of the Official Secrets Act
surrounding the wartime work at Bletchley Park made it impossible for
Turing to explain the basis of his analysis of how a computer
installation involving human operators would work.
This led to delays in starting the project and he became disillusioned.
In late 1947 he returned to Cambridge for a sabbatical year during
which he produced a seminal work on Intelligent Machinery that was not published in his lifetime. While he was at Cambridge, the Pilot ACE
was being built in his absence. It executed its first program on 10 May
1950, and a number of later computers around the world owe much to it,
including the English Electric DEUCE and the American Bendix G-15. The full version of Turing's ACE was not built until after his death.
According to the memoirs of the German computer pioneer Heinz Billing from the Max Planck Institute for Physics, published by Genscher, Düsseldorf, there was a meeting between Turing and Konrad Zuse. It took place in Göttingen
in 1947. The interrogation had the form of a colloquium. Participants
were Womersley, Turing, Porter from England and a few German researchers
like Zuse, Walther, and Billing (for more details see Herbert Bruderer,
Konrad Zuse und die Schweiz).
In 1948, Turing was appointed reader in the Mathematics Department at the Victoria University of Manchester.
A year later, he became deputy director of the Computing Machine
Laboratory, where he worked on software for one of the earliest stored-program computers—the Manchester Mark 1.
Turing wrote the first version of the Programmer's Manual for this
machine, and was recruited by Ferranti as a consultant in the
development of their commercialised machine, the Ferranti Mark 1. He
continued to be paid consultancy fees by Ferranti until his death. During this time, he continued to do more abstract work in mathematics, and in "Computing Machinery and Intelligence" (Mind, October 1950), Turing addressed the problem of artificial intelligence, and proposed an experiment that became known as the Turing test,
an attempt to define a standard for a machine to be called
"intelligent". The idea was that a computer could be said to "think" if a
human interrogator could not tell it apart, through conversation, from a
human being.
In the paper, Turing suggested that rather than building a program to
simulate the adult mind, it would be better to produce a simpler one to
simulate a child's mind and then to subject it to a course of education.
A reversed form of the Turing test is widely used on the Internet; the CAPTCHA test is intended to determine whether the user is a human or a computer.
In 1948, Turing, working with his former undergraduate colleague, D.G. Champernowne, began writing a chess program for a computer that did not yet exist. By 1950, the program was completed and dubbed the Turochamp. In 1952, he tried to implement it on a Ferranti Mark 1,
but lacking enough power, the computer was unable to execute the
program. Instead, Turing "ran" the program by flipping through the pages
of the algorithm and carrying out its instructions on a chessboard,
taking about half an hour per move. The game was recorded. According to Garry Kasparov, Turing's program "played a recognizable game of chess". The program lost to Turing's colleague Alick Glennie, although it is said that it won a game against Champernowne's wife, Isabel.
His Turing test was a significant, characteristically
provocative, and lasting contribution to the debate regarding artificial
intelligence, which continues after more than half a century.
Pattern formation and mathematical biology
When Turing was 39 years old in 1951, he turned to mathematical biology, finally publishing his masterpiece "The Chemical Basis of Morphogenesis" in January 1952. He was interested in morphogenesis,
the development of patterns and shapes in biological organisms. He
suggested that a system of chemicals reacting with each other and
diffusing across space, termed a reaction–diffusion system, could account for "the main phenomena of morphogenesis". He used systems of partial differential equations
to model catalytic chemical reactions. For example, if a catalyst A is
required for a certain chemical reaction to take place, and if the
reaction produced more of the catalyst A, then we say that the reaction
is autocatalytic,
and there is positive feedback that can be modelled by nonlinear
differential equations. Turing discovered that patterns could be created
if the chemical reaction not only produced catalyst A, but also
produced an inhibitor B that slowed down the production of A. If A and B
then diffused through the container at different rates, then you could
have some regions where A dominated and some where B did. To calculate
the extent of this, Turing would have needed a powerful computer, but
these were not so freely available in 1951, so he had to use linear
approximations to solve the equations by hand. These calculations gave
the right qualitative results, and produced, for example, a uniform
mixture that oddly enough had regularly spaced fixed red spots. The
Russian biochemist Boris Belousov
had performed experiments with similar results, but could not get his
papers published because of the contemporary prejudice that any such
thing violated the second law of thermodynamics. Belousov was not aware of Turing's paper in the Philosophical Transactions of the Royal Society.
Although published before the structure and role of DNA
was understood, Turing's work on morphogenesis remains relevant today
and is considered a seminal piece of work in mathematical biology.
One of the early applications of Turing's paper was the work by James
Murray explaining spots and stripes on the fur of cats, large and small.
Further research in the area suggests that Turing's work can partially
explain the growth of "feathers, hair follicles, the branching pattern
of lungs, and even the left-right asymmetry that puts the heart on the
left side of the chest". In 2012, Sheth, et al. found that in mice, removal of Hox genes
causes an increase in the number of digits without an increase in the
overall size of the limb, suggesting that Hox genes control digit
formation by tuning the wavelength of a Turing-type mechanism. Later papers were not available until Collected Works of A. M. Turing was published in 1992.
A study conducted in 2023 confirmed Turing's mathematical model hypothesis. Presented by the American Physical Society, the experiment involved growing chia seeds
in even layers within trays, later adjusting the available moisture.
Researchers experimentally tweaked the factors which appear in the
Turing equations, and, as a result, patterns resembling those seen in
natural environments emerged. This is believed to be the first time that
experiments with living vegetation have verified Turing's mathematical
insight.
Personal life
Treasure
In the 1940s, Turing became worried about losing his savings in the
event of a German invasion. In order to protect it, he bought two silver bars
weighing 3,200 oz (90 kg) and worth £250 (in 2022, £8,000 adjusted for
inflation, £48,000 at spot price) and buried them in a wood near
Bletchley Park.
Upon returning to dig them up, Turing found that he was unable to break
his own code describing where exactly he had hidden them. This, along
with the fact that the area had been renovated, meant that he never
regained the silver.
Engagement
In 1941, Turing proposed marriage to Hut 8 colleague Joan Clarke,
a fellow mathematician and cryptanalyst, but their engagement was
short-lived. After admitting his homosexuality to his fiancée, who was
reportedly "unfazed" by the revelation, Turing decided that he could not
go through with the marriage.
Homosexuality and indecency conviction
In January 1952, Turing was 39 when he started a relationship with Arnold Murray, a 19-year-old unemployed man. Just before Christmas, Turing was walking along Manchester's Oxford Road when he met Murray just outside the Regal Cinema
and invited him to lunch. On 23 January, Turing's house was burgled.
Murray told Turing that he and the burglar were acquainted, and Turing
reported the crime to the police. During the investigation, he
acknowledged a sexual relationship with Murray. Homosexual acts were
criminal offences in the United Kingdom at that time, and both men were charged with "gross indecency" under Section 11 of the Criminal Law Amendment Act 1885. Initial committal proceedings
for the trial were held on 27 February during which Turing's solicitor
"reserved his defence", i.e., did not argue or provide evidence against
the allegations. The proceedings were held at the Sessions House in Knutsford.
Turing was later convinced by the advice of his brother and his own solicitor, and he entered a plea of guilty. The case, Regina v. Turing and Murray, was brought to trial on 31 March 1952.
Turing was convicted and given a choice between imprisonment and
probation. His probation would be conditional on his agreement to
undergo hormonal physical changes designed to reduce libido, known as "chemical castration". He accepted the option of injections of what was then called stilboestrol (now known as diethylstilbestrol or DES), a synthetic oestrogen; this feminization of his body was continued for the course of one year. The treatment rendered Turing impotent and caused breast tissue to form. In a letter, Turing wrote that "no doubt I shall emerge from it all a different man, but quite who I've not found out".Murray was given a conditional discharge.
Turing's conviction led to the removal of his security clearance
and barred him from continuing with his cryptographic consultancy for
the Government Communications Headquarters (GCHQ), the British signals intelligence
agency that had evolved from GC&CS in 1946, though he kept his
academic job. His trial took place only months after the defection to
the Soviet Union of Guy Burgess and Donald Maclean in summer 1951 after which the Foreign Office started to consider anyone known to be homosexual as a potential security risk.
Turing was denied entry into the United States after his conviction in 1952, but was free to visit other European countries.
In the summer of 1952 he visited Norway which was more tolerant of
homosexuals. Among the various men he met there was one named Kjell
Carlson. Kjell intended to visit Turing in the UK but the authorities
intercepted Kjell's postcard detailing his travel arrangements and were
able to intercept and deport him before the two could meet.
It was also during this time that Turing started consulting a
psychiatrist, Dr Franz Greenbaum, with whom he got on well and
subsequently becoming a family friend.
Death
A blue plaque on the house at 43 Adlington Road, Wilmslow, where Turing lived and died
On 8 June 1954, at his house at 43 Adlington Road, Wilmslow,
Turing's housekeeper found him dead. A post mortem was held that
evening which determined that he had died the previous day at the age of
41 with Cyanide poisoning cited as the cause of death. When his body was discovered, an apple lay half-eaten beside his bed, and although the apple was not tested for cyanide, it was speculated that this was the means by which Turing had consumed a fatal dose.
Turing's brother John identified the body the following day and
took the advice given by Dr. Greenbaum to accept the verdict of the
inquest as there was little prospect of establishing that the death was
accidental. The inquest was held the following day which determined the cause of death to be suicide. Turing's remains were cremated at Woking Crematorium just two days later on 12 June 1954 with just three people attending and his ashes were scattered in the gardens of the crematorium, just as his father's had been.
Turing's mother was on holiday in Italy at the time of his death and
returned home after the inquest. She never accepted the verdict of
suicide.
Andrew Hodges and another biographer, David Leavitt, have both speculated that Turing was re-enacting a scene from the Walt Disney film Snow White and the Seven Dwarfs
(1937), his favourite fairy tale. Both men noted that (in Leavitt's
words) he took "an especially keen pleasure in the scene where the
Wicked Queen immerses her apple in the poisonous brew".
Philosopher Jack Copeland
has questioned various aspects of the coroner's historical verdict. He
suggested an alternative explanation for the cause of Turing's death:
the accidental inhalation of cyanide fumes from an apparatus used to electroplate gold onto spoons. The potassium cyanide was used to dissolve the gold.
Turing had such an apparatus set up in his tiny spare room. Copeland
noted that the autopsy findings were more consistent with inhalation
than with ingestion of the poison. Turing also habitually ate an apple
before going to bed, and it was not unusual for the apple to be
discarded half-eaten.
Furthermore, Turing had reportedly borne his legal setbacks and hormone
treatment (which had been discontinued a year previously) "with good
humour" and had shown no sign of despondency before his death. He even
set down a list of tasks that he intended to complete upon returning to
his office after the holiday weekend. Turing's mother believed that the ingestion was accidental, resulting from her son's careless storage of laboratory chemicals.
Biographer Andrew Hodges theorised that Turing deliberately left the
nature of his death ambiguous in order to shield his mother from the
knowledge that he had killed himself.
It has been suggested that Turing's belief in fortune-telling may have caused his depressed mood.
As a youth, Turing had been told by a fortune-teller that he would be a
genius. In mid-May 1954, shortly before his death, Turing again decided
to consult a fortune-teller during a day-trip to St Annes-on-Sea with the Greenbaum family. According to the Greenbaums' daughter, Barbara:
But it was a lovely sunny day and Alan was in a cheerful mood and off
we went... Then he thought it would be a good idea to go to the Pleasure Beach at Blackpool.
We found a fortune-teller's tent and Alan said he'd like to go in[,] so
we waited around for him to come back... And this sunny, cheerful
visage had shrunk into a pale, shaking, horror-stricken face. Something
had happened. We don't know what the fortune-teller said but he
obviously was deeply unhappy. I think that was probably the last time we
saw him before we heard of his suicide.
In August 2009, British programmer John Graham-Cumming started a petition urging the British government to apologise for Turing's prosecution as a homosexual. The petition received more than 30,000 signatures. The prime minister, Gordon Brown,
acknowledged the petition, releasing a statement on 10 September 2009
apologising and describing the treatment of Turing as "appalling":
Thousands of people have come
together to demand justice for Alan Turing and recognition of the
appalling way he was treated. While Turing was dealt with under the law
of the time and we can't put the clock back, his treatment was of course
utterly unfair and I am pleased to have the chance to say how deeply
sorry I and we all are for what happened to him ... So on behalf of the
British government, and all those who live freely thanks to Alan's work I
am very proud to say: we're sorry, you deserved so much better.
In December 2011, William Jones and his member of Parliament, John Leech, created an e-petition requesting that the British government pardon Turing for his conviction of "gross indecency":
We ask the HM Government to grant a
pardon to Alan Turing for the conviction of "gross indecency". In 1952,
he was convicted of "gross indecency" with another man and was forced
to undergo so-called "organo-therapy"—chemical castration. Two years
later, he killed himself with cyanide, aged just 41. Alan Turing was
driven to a terrible despair and early death by the nation he'd done so
much to save. This remains a shame on the British government and British
history. A pardon can go some way to healing this damage. It may act as
an apology to many of the other gay men, not as well-known as Alan
Turing, who were subjected to these laws.
The petition gathered over 37,000 signatures, and was submitted to Parliament by the Manchester MP John Leech but the request was discouraged by Justice Minister Lord McNally, who said:
A posthumous pardon was not
considered appropriate as Alan Turing was properly convicted of what at
the time was a criminal offence. He would have known that his offence
was against the law and that he would be prosecuted. It is tragic that
Alan Turing was convicted of an offence that now seems both cruel and
absurd—particularly poignant given his outstanding contribution to the
war effort. However, the law at the time required a prosecution and, as
such, long-standing policy has been to accept that such convictions took
place and, rather than trying to alter the historical context and to
put right what cannot be put right, ensure instead that we never again
return to those times.
John Leech, the MP for Manchester Withington (2005–15), submitted several bills to Parliament
and led a high-profile campaign to secure the pardon. Leech made the
case in the House of Commons that Turing's contribution to the war made
him a national hero and that it was "ultimately just embarrassing" that
the conviction still stood.
Leech continued to take the bill through Parliament and campaigned for
several years, gaining the public support of numerous leading
scientists, including Stephen Hawking. At the British premiere of a film based on Turing's life, The Imitation Game, the producers thanked Leech for bringing the topic to public attention and securing Turing's pardon.
Leech is now regularly described as the "architect" of Turing's pardon
and subsequently the Alan Turing Law which went on to secure pardons for
75,000 other men and women convicted of similar crimes.
On 26 July 2012, a bill was introduced in the House of Lords
to grant a statutory pardon to Turing for offences under section 11 of
the Criminal Law Amendment Act 1885, of which he was convicted on 31
March 1952. Late in the year in a letter to The Daily Telegraph, the physicist Stephen Hawking and 10 other signatories including the Astronomer RoyalLord Rees, President of the Royal Society Sir Paul Nurse, Lady Trumpington (who worked for Turing during the war) and Lord Sharkey (the bill's sponsor) called on Prime Minister David Cameron to act on the pardon request. The government indicated it would support the bill, and it passed its third reading in the House of Lords in October.
At the bill's second reading in the House of Commons on 29 November 2013, Conservative MP Christopher Chope objected to the bill, delaying its passage. The bill was due to return to the House of Commons on 28 February 2014, but before the bill could be debated in the House of Commons, the government elected to proceed under the royal prerogative of mercy. On 24 December 2013, Queen Elizabeth II signed a pardon for Turing's conviction for "gross indecency", with immediate effect. Announcing the pardon, Lord Chancellor Chris Grayling
said Turing deserved to be "remembered and recognised for his fantastic
contribution to the war effort" and not for his later criminal
conviction.The Queen officially pronounced Turing pardoned in August 2014. The Queen's action is only the fourth royal pardon granted since the conclusion of the Second World War.
Pardons are normally granted only when the person is technically
innocent, and a request has been made by the family or other interested
party; neither condition was met in regard to Turing's conviction.
In September 2016, the government announced its intention to
expand this retroactive exoneration to other men convicted of similar
historical indecency offences, in what was described as an "Alan Turing law". The Alan Turing law is now an informal term for the law in the United Kingdom, contained in the Policing and Crime Act 2017, which serves as an amnesty law
to retroactively pardon men who were cautioned or convicted under
historical legislation that outlawed homosexual acts. The law applies in
England and Wales.
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