Joan Clarke

Joan Clarke went to Cambridge to study Mathematics, and was awarded a double First in 1940. One of her supervisors was Gordon Welchman who persuaded her to come to Bletchley Park after completing her studies. On arrival she was not put into Hut 6 with Welchman, but instead was assigned to work with Turing in Hut 8. Turing was a friend of Joan's older brother Michael. She became adept at 'Banburismus', an application of Bayesian statistics which made large savings of processed time on the Bombes. She remained in Hut 8 for the rest of the war.

Joan became engaged to Turing in the spring of 1941: their families were informed, but it was kept secret from their colleagues. The engagement was broken off later that year because Turing was gay, but they remained friends for the rest of his life. Joan was one of the first people he wrote to after his arrest.

After the war, Joan became engaged to an Army integree, Lt Col Jock Murray, who she married in 1952. She rejoined GCHQ in 1962, working in cryptanalysis for the rest of her career. After retirement she was asked to work with Sir Harry Hinsley, who was writing the official history British Intelligence in the Second World War, correcting the first inaccurate account of the respective contributions of the British, the French and the Poles to the solution of Enigma.