Alan Turing

This man would probably not be recognisable to a great many people. His name might help with that. For some of us, at least.

We should all know his name, if not his face. Alan Turing was responsible for saving hundreds of thousands of lives during the Second World War. And how did he do this? He cracked the infamous Nazi Enigma code - the code that was considered impossible to decipher - with the help of a forerunner of a modern day computer.

Alan carried out his work in top secret at Bletchley Park, and once completed he and his team were able to listen in on the radio intercepts of the German military. Positions, troop strengths, dates and times...all were known to them. This information was relayed to the British Government, who in turn could weaponise the information and save countless Allied lives.

But there was just one problem. Alan Turing was homosexual. And this was illegal in the UK at the time.

When this was revealed shortly after the war, Turing was made to take "homosexual-inhibitors": drugs that would 'cure' him of his 'illness'. After a prolonged period of sustained assault on his body, Alan fell into a deep depression and took his own life. He was officially pardoned by the Queen in 2016.

Timeline

• 23 June 1912: Alan Mathison Turing was born in London.
• 1926: Aged 14, he was sent to Sherborne School in Dorset. His first day of term coincided with the 1926 General Strike. Turing was so determined not to miss his first day of school that he cycled the 97km from his home in Southampton. His teachers worried that he leaned too heavily towards maths and science, at the expense of the classics. The headmaster wrote to his parents: "If he is to be solely a scientific specialist, he is wasting his time at a public school".
• 1930: Turing's close school friend Christopher Morcom dies suddenly from bovine tuberculosis. Turing renounces his religious faith and becomes an atheist.
• 1931: Turing goes to study Mathematics at King's College, Cambridge.
• 1936: Turing published his paper On Computable Numbers and an Application to the Entscheidungsproblem (decision problem) in which he outlines the Universal Machine, which later became known as the Turing Machine. This was an idealised computing device that is capable of performing any mathematical computation that can be represented as an algorithm.
• September 1938: Turing started to work part-time at the Government Code and Cypher School.
• 1939: The day after war is declared in September 1939, Turing arrives at Bletchley Park. There he works with Gordon Welchman to develop the Bombe, a device for decrypting the messages sent by Germans using their Enigma machines. The Bombe built on a machine that the Polish had already made, called the Bomba Kryptlogiczna. Turing used statistical techniques to optimise the trial of different possibilities in the code-breaking process using probability.
• 1941-43: Turing and colleagues manage to break the more complicated German Naval Enigma system. This is extremely helpful for the Allies during the Battle of the Atlantic as it could help them avoid the fearsome German U-boats, which had been responsible for sinking more than 700 Allied ships with 2.3 million tons of vital cargo.
• 1949: Turing became deputy director of the Computing Laboratory at Manchester University, working on software for one of the earliest stored program computers – the Manchester Mark 1. He also explored the problem of artificial intelligence and proposed an experiment (in his seminal paper Computing Machinery and Intelligence) which became that attempted to define a standard for machine intelligence, which would later become known as the Turing test. The core 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. Turing also worked with his former colleague D G Champernowne on a chess program for a computer that did not exist yet.
• 1952: Without a computer powerful enough to execute his chess program, Turing played a game in which he simulated the computer, taking about half an hour to perform each move. The program lost to Turing's colleague Alick Glennie, but won against Champernowne's wife.
• January 1952: Turing meets a man called Arnold Murray and invites him over to his house. Murray visits Turing's house on a number of occasions, staying the night. Murray later helps an accomplice break into Turing's house. Turing reports the crime and admits having a sexual relationship with Murray. Homosexual acts are illegal in the UK and so both were charged with gross indecency. Turing is given the choice of being imprisoned or chemically castrated with oestrogen hormone injections. He chooses the latter. Turing's conviction means his security clearance is removed which means he is barred from his cryptopgraphic consultancy for the British government.
• 08 June 1954: Turing's cleaner finds him dead. It appears that Turing poisoned himself using a cyanide-laced apple.