Alan Turing

**Alan Turing** was a codebreaker of the Government Code and Cypher School at Bletchley Park. Under the direction of Commander Alastair Denniston, he joined the cryptography team of Hugh Alexander, John Cairncross, Peter Hilton, Keith Furman, and Charles Richards. The team was trying to analyze the Enigma machine, which the Nazis use to send coded messages.

Turing was difficult to work with, and considered his colleagues inferior; he worked alone to design a machine to decipher Enigma messages. After Denniston refused to fund the construction of the machine, Turing wrote to Prime Minister Winston Churchill, who put Turing in charge of the team and funded the machine. Turing fired Furman and Richards and placed a difficult crossword in newspapers to find replacements. Joan Clarke, a Cambridge graduate, passed Turing's test but her parents would not allow her to work with the male cryptographers. Turing arranged for her to live and work with the female clerks who intercept the messages and shared his plans with her. With Clarke's help, Turing warmed to the other colleagues, who began to respect him.

Turing's machine, which he named Christopher, was constructed, but could not determine the Enigma encryption settings quickly enough; the Germans reset them each day. Denniston ordered it to be destroyed and Turing fired, but the other cryptographers threatened to leave if Turing went. After Clarke planned to leave on the wishes of her parents, Turing proposed marriage, which she accepted. During their engagement party, Turing confirmed his homosexuality to Cairncross, who warned him to keep it secret. After overhearing a conversation with a female clerk about messages she received from the same German coder, Turing had an epiphany, realising he could program the machine to decode words he already knows exist in certain messages. One German coder always opened his first message with a standard plaintext German script. That revealed enough of the day's Enigma code that Christopher could quickly decode all the day's messages. After he recalibrated the machine, it quickly decoded a message and the cryptographers celebrated.

They learned a convoy was about to be attacked, but Turing realised that if they suddenly rerouted the convoy and attacked the U-boats, the Germans would realize Enigma was compromised and change the machinery. Therefore, the team at Bletchley Park could not act on every decoded message and chose not to save the convoy, despite desperate pleas from Peter, whose brother was a sailor serving on one of the ships. Turing created a statistical model to indicate which warnings to send to maximize destruction and minimize discovery.

Turing discovered that Cairncross was a Soviet spy. When Turing confronted him, Cairncross argued that the Soviets were allies working for the same goals, and threatened to retaliate by disclosing Turing's sexuality. When the top MI6 agent Stewart Menzies appeared to threaten Clarke, Turing revealed that Cairncross was a spy. Menzies revealed he knew this already and planted the messages Cairncross leaked to the Soviets for British benefit. Fearing for her safety, Turing told Clarke to leave Bletchley Park, revealing that he was a homosexual. Clarke stated she always suspected but insisted they would have been happy together anyway. Turing then told her he never cared for her, and only used her for her cryptography skills. Heartbroken, she decided to stay anyway, deeming this the single most important task she would undertake, and she refused to cow to what Turing or her parents wanted her to do, or think of her decisions. After the war, Menzies told the cryptographers to destroy their work, because MI6 wanted governments to think they had unbreakable code machines. He told team that they should never see one another again or share what they had done.

In 1952, Turing was convicted of gross indecency and, in lieu of a prison sentence, underwent chemical castration so he could continue his work. Clarke visited him in his home and witnessed his physical and mental deterioration. She comforted him by saying that his work saved millions of lives.

A year after the government-mandated hormonal therapy, Turing died by suicide on 7 June 1954. In 2013, Queen Elizabeth II granted Turing a posthumous Royal Pardon, honouring his work which would eventually go on to create the modern computer.

## Notes

* He is a fictional portrayal of the real Alan Mathison Turing. [1]