The Imitation Game (IG) is a great movie which has brought a lot of attention to Alan Turing but if you like it, you should also watch the 2013 film Codebreaker (CB), which can be streamed on Netflix. Remarkably these two films give almost disjoint accounts of his life. I guess at this point I should give a SPOILER ALERT that I am about to describe some pivotal events in his life, which are revealed in the movie. A couple of the revelations might spoil your enjoyment but you have been warned.

CB spends a fair amount of time on Turing’s work on computability. The movie even shows a copy of the 1928 article by David Hilbert’s paper “On Computable Numbers, with an Application to the Entscheidungsproblem (Decision Problem).” It goes into some detail describing what a Turing machine is. As many of you know, he proved that such a machine would be capable of performing any conceivable mathematical computation if it were representable as an algorithm. The movie doesn’t go on to mention that Turing showed that the halting problem for Turing machines was undecidable, but that’s OK since Von Neumann acknowledged that the central concept of the modern computer was due to this paper. Not a bad result for an undergraduate at King’s College.

IG spends a lot of telling the story of Turing’s role in decrypting messages sent by the Enigma machine. At Bletchley Park, Turing built an electromechanical machine, the bombe, that could help break Enigma more effectively than the Polish bomba kryptologiczna, from which its name was derived.

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 of the order of 10 ¹⁹ states, or 10²² for the four-rotor U-boat variant, the bombe performed a chain of logical deductions based on the crib, implemented electrically. It detected when a contradiction had occurred, and ruled out that setting, moving on to the next. A brute force search of such a large space was not practical. According to the movie, a breakthrough came when they realized that the Germans sent out a weather report each day at 6AM that ended with the phrase Heil Hitler.

Both movies mention the fact that in 1941, Turing proposed marriage to Hut 8 co-worker Joan Clarke (played by Keira Knightley in IG), 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. (In real life Joan Clark was somewhat less attractive.)

Despite some scenes of Turing running long distances (in CB if I recall correctly) neither movie mentions that while working at Bletchley, Turing, who was a talented long-distance runner, occasionally ran the 40 miles to London when he was needed for high-level meetings. In addition, he was capable of world-class marathon standards. Turing tried out for the 1948 British Olympic team. His time for the marathon was only 11 minutes slower than British silver medalist Thomas Richards’ Olympic race time of 2 hours 35 minutes.

Going back in time, a third key event in Turing’s life occurred at Sherborne School, which Turing entered in 1926 at the age of 13. At Sherborne, Turing formed an important friendship with fellow pupil Christopher Morcom, which provided inspiration in Turing’s future endeavours. However, the friendship 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. This event shattered Turing’s religious faith and he became an atheist

Neither movie has anything to say about his ground breaking paper on The Chemical Basis of Morphogensis published in 1952, which put forth his ideas about pattern formation in development. However, both movies cover the fact that in January 1952, Turing, then 39, started a relationship with Arnold Murray, a 19-year old unemployed man. A burglary brought the police to his house, the police discovered their relationship, and the fact that a valuable watch was missing was forgotten.

Homosexual acts were criminal in the UK at that time.  Turing was convicted and given a choice between imprisonment and probation, which would be conditional on his agreement to undergo hormonal treatment designed to reduce libido. He accepted the option of treatment via injections of stilboestrol, (CB shows you the bottle of tablets), a synthetic estrogen. The treatment rendered Turing impotent and caused gynaecomastia, growing female breasts.

On 8 June 1954, Turing’s housekeeper found him dead. He had died the previous day. A post-mortem examination established that the cause of death was cyanide poisoning. 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 a fatal dose was consumed.

CB spends more time on the impact of estrogen therapy than IG, which has one brief scene with Turing and Joan Clarke one year after his conviction, in which he shows tremors in his movements. CB makes the point that the hormones did more stop his sex drive they also affected his ability to think. This part of the story is told in IG through a conversation between Turing and policeman, which explains the title Imitation Game.  In “Computing machinery and intelligence,” Turing addressed the problem of artificial intelligence, and proposed an experiment which 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.

The achievements listed above do not exhaust all the extraordinary things Turing did in his 41 years. IG portrays him as an overbearing individual who could not understand other people’s feelings. Today we would say he was on the autism spectrum. CB tells the story of a brilliant man who just happened to be gay. Independent of which of these (if either) is true, IG says in its closing moments that cracking the Enigma Code shortened the war by two years and SAVED 14 MILLION LIVES.

Given this and his impressive intellectual achievements, the decision to chemically castrate Turing, which caused his death was insane, as is the fact that it took until 2009 for the British Government to apologize. With an important decision on Gay Marriage looming in the Supreme Court, this is an important example to keep in mind.  When homophobes and bigots quote the Bible to justify that marriage is only allowed between one man and one woman, we should ask “What would Jesus do?”

For more on Turing you could buy the book Alan Turing: The Enigma written by Andrew Hodges and Douglas Hofstadter or visit www.turing.ord.uk/, maintained by Hodges.