Z Watch in Hut 4, part I / Alec Dakin. The Z Watch in Hut 4, part II / Walter Eytan -- Italian naval decrypts / Patrick Wilkinson. Naval Section VI / Vivienne Alford. Anglo-American signals intelligence co-operation / Telford Taylor. An American at Bletchley Park / Robert M. Slusser. Bletchley Park, the Admiralty, and naval Enigma / F.H. Hinsley -- Enigma: The Enigma machine : its mechanism and use / Alan Stripp. Hut 6 : early days / Stuart Milner-Barry. Hut 6 : 1941-1945 / Derek Taunt. Hut 8 and naval Enigma, part I / Joan Murray. Hut 8 and naval Enigma, part II / Rolf Noskwith. The Abwehr Enigma / Peter Twinn. The bombers / Diana Payne -- Fish: An introduction to Fish / F.H. Hinsley. Enigma and Fish / Jack Good. The Tunny machine / Ken Halton. Operation Tunny / Gil Hayward -- Field ciphers and tactical codes: Recollections of Bletchley Park, France, and Cairo / Henry Dryden. Army Ultra's poor relations / Noel Currer-Briggs. Navy Ultra's poor relations / Christopher Morris. Tactical signals of the German Air Force / Peter Gray Lucas -- Japanese codes: Japanese naval codes / Michael Loewe. Bedford--Bletchley--Kilindini--Colombo / Hugh Denham. Japanese military codes / Maurice Wiles. Japanese Army Air Force codes at Bletchley Park and Delhi / Alan Stripp. Recollections of temps perdu at Bletchley Park / Carmen Blacker. Appendix : how the Bletchley Park buildings took shape / Bob Watson.