Alan Turing was one of the greatest British minds of the last century. He died 53 years ago but it was only yesterday that a statue was unveiled to him at the site of his greatest triumph, Bletchley Park, thanks to the bequest of a American billionaire (there is another statue in Manchester). Long after his death, Turing's role in breaking the code of the Atlantic U-boat Enigma machine in 1942 remained secret. But hut eight of the wartime precursor to GCHQ was where the battle of the Atlantic was won. A greater prize lay beyond that. As his biographer Andrew Hodges has written, the conjunction of Turing's theories, his collaboration with Max Newman, and the presence of telephone engineers pressed into the effort of speeding up calculating machines, led to the development of the computer. Back in 1936, Turing conceived of a machine able to perform elementary operations on symbols punched on paper tape. For this, he is now recognised as the founder of the modern theory of computation. But Turing never benefited from the revolution that he started. In 1952, he was convicted of having a sexual relationship with another man, to which he made no defence other than to say he saw nothing wrong in his actions. The conviction robbed him of his security clearance for GCHQ, for which he still worked, and made him the target for surveillance at the height of the cold war. He died after eating an apple laced with cyanide. The symbol of the half-eaten apple lives on to this day.