Alan Turing (1912-54). Computer illustration of the British mathematician Alan Turing. In 1937, Turing described a theoretical computer (a Turing machine) in rigorous mathematical terms, formalising the previously vague concept of computability. During the Second World War he worked as a code breaker at Bletchley Park, Britain's codebreaking centre. In 1939-40 Turing and Cambridge mathematician, Gordon Welchman, designed the British Bombe, which could break any Enigma-enciphered message. In later years he worked on Artificial Intelligence, devising the Turing test to decide whether a computer can be thought of as truly 'intelligent'. Turing committed suicide when prosecuted for his homosexuality, a criminal offence at the time.