From 1939, British intelligence collected top mathematicians and code-breakers at Bletchley Park outside of London to assist in breaking the German codes of the Enigma machine. There, Turing led a mix of individuals attempting to build on work that had been conducted by the Poles. Bletchley Park was ultimately able to read all German encrypted radio traffic, although not in real time. Nonetheless, this work was immensely successful, and the information it provided, code-named Top Secret ultra, proved vital to the Allied victory in World War II. Turing left Bletchley Park in 1943 to develop a speech encipherment system.
Following the war, he worked on the development of the first electronic (as opposed to mechanical) computers and wrote papers that are considered the foundation of today's field of artificial intelligence. Arrested, tried, and convicted in 1952 for homosexual activities, Turing acceded to a regimen of estrogen injections in lieu of imprisonment and continued with his research while under observation by members of a security detail, who were vexed when he took a Greek vacation in 1953. Turing, whose mother claimed he often experimented with poisonous chemicals, died on 4 June 1951 at Winslow, Cheshire, England, after eating part of an apple laced with potassium cyanide; an inquest deemed his death a suicide.
Hodges, Andrew. Alan Turing: The Enigma. London: Burnett Books, 1983.; Lewin, Ronald. Ultra Goes to War. New York: McGraw-Hill, 1978.; Winterbotham, F. W. The Ultra Secret. New York: Harper and Row, 1974.