On 4 September 1939 the day after Britain declared war on Germany, Turing reported to Bletchley Park, the wartime station of the Government Code and Cypher School and forerunner of GCHQ. At Bletchley, Turing led a team whose ingenuity and intellect were turned to the task of breaking German ciphers. One of Turing’s main contributions whilst there was to invent the Bombe, an electromechanical machine used to find the daily settings of the Enigma machine. A fully functional rebuild of the Bombe can be found today at Bletchley Park, along with the excellent Turing exhibition, I encourage you to visit.