Series examining the work of the code-breakers at Bletchley Park, near Milton Keynes, during World War 2. Uses interviews with staff and dramatic reconstructions of events. In four parts: 1) The Keys to the Reich: deciphering messages encrypted on Germany’s Enigma machine; 2) The Goose That Laid the Golden Eggs: the role of Station X in the air and sea battles of 1941 and the part played by Alan Turing in cracking Germany’s naval messages; 3) The Ultra Secret: Turing’s development of the Bombe, a machine used to automate the code-breaking process and British forces time to counter the enemy’s immediate plans; 4) The War of the Machines: Enigma and Lorenz cipher machines; role of Station X in the Battle of the Atlantic and D-Day landings; the computer developed to help break codes; the lighter side of life at Bletchley Park; the future of those who left at the end of the war