Joan Clarke

Cryptanalyst in Hut 8 at Bletchley Park and, from 1944, its deputy head. Born on 24 June 1917 in West Norwood, London. She read mathematics at Newnham College, Cambridge, and took a double first — but was not awarded the degree, as no woman at Cambridge was until 1948. She was recruited to Bletchley Park in 1940 by Gordon Welchman, who had taught her at Cambridge. She began in the women's section on routine work and was quickly moved into Hut 8, on naval Enigma. She mastered Banburismus, Turing's demanding statistical method, which only a handful of people could use, and applied it daily against the U-boat cipher. In 1944 she became deputy head of Hut 8. Her position illustrates the arrangements of the time more plainly than any description: doing a cryptanalyst's work, she was graded as a "linguist", because no pay grade for a woman doing that work existed. On the form she noted that she had no languages. She was engaged to Alan Turing for a time; the engagement was broken off and the friendship lasted the rest of his life. She stayed on at GCHQ after the war and was appointed MBE in 1946. She died on 4 September 1996. Her work became widely known only decades later — as did that of most of Bletchley Park's staff, bound to silence by the Official Secrets Act.