After three decades shrouded in secrecy, there now appear to be few stories untold about Bletchley Park, the code-breaking centre in Buckinghamshire whose work is thought to have shortened the Second World War by up to three years. Historians have had huge fun with a cast of 12,000, ranging from mathematicians to Egyptologists. Dillwyn Knox, a Cambridge classical papyrus expert, used to work in his pyjamas, while Alan Turing, the pioneer of the computer age, liked to take his cat on walks. When Churchill, an avid supporter, visited, he said to the head of MI6, “When I told you to leave no stone unturned recruiting for this place, I didn’t expect you to take me literally.” Much, too, has been written about the impact of the Bletchley alumni after the war. Michael Smith, author of The Secrets of Station X, points out that they included the chief prosecutor at the Nuremburg Trials, the music directors of Sadler’s Wells and the BBC, the founder of Amnesty International, and John Cairncross, the traitor.