NOTES TO PAGES 109–112 | 493
their secrets: Alastair Denniston’s account of the July 1939 meeting at Pyry’, Cryptologia, 30 (2006),
294–305.)- M. Rejewski, ‘How Polish mathematicians deciphered the Enigma’ (transl. J. Stepenske), Annals of the
History of Computing, 3 (1981), 213–34, p. 227. - P. Twinn, ‘The Abwehr Enigma’, in Hinsley & Stripp (1993), pp. 126–7; Denniston (Note 2), pp. 4–5;
A. D. Knox, ‘Warsaw’, 4 August 1939, NA HW25/12. - For a detailed account of the Polish bomba, see B. J. Copeland, ‘Enigma’, in The Essential Turing,
pp. 235–46; and D. Davies, ‘The Bombe—a remarkable logic machine’, Cryptologia, 23 (1999), 108–38. - J. Murray (née Clarke), ‘A personal contribution to the Bombe story’, NSA Technical Journal, 20(4)
(Fall 1975), 41–6, p. 42. - ‘Operations of the 6812th Signal Security Detachment, ETOUSA’ (1 October 1944), US National
Archives and Records Administration, RG 457, Entry 9032, Historic Cryptographic Collection, pre-
World War I through World War II, Box 970, no. 2943, p. 5; I am grateful to Frode Weierud for
supplying me with a copy of this document. - Rejewski’s diagram is in B. Johnson, The Secret War, Pen & Sword (2004), p. 316. The suggestion that
the component adjacent to the drive shaft is a magnet is due to David Link. - W. Kozaczuk, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the
Allies in World War Two (transl. by C. Kasparek), Arms and Armour Press (1984), p. 63. - Michael Foot reported this in answer to a question at a Sigint conference in Oxford (information from
Ralph Erskine). - M. Rejewski, ‘How the Polish mathematicians broke Enigma’, in Kozaczuk (Note 9), p. 267.
- Denniston (Note 2), p. 4.
- Copeland, ‘Enigma’ (Note 5), p. 246.
- ‘Enigma – Position’ and ‘Naval Enigma Situation’, notes dated 1 November 1939 and signed by Knox,
Twinn, Welchman, and Turing, NA HW14/2. - For more information about the bombe, see A. M. Turing, ‘Bombe and Spider’ (Turing 1940),
Copeland, ‘Enigma’ (Note 5), pp. 246–57; F. Carter, ‘The Turing Bombe’, Rutherford Journal for the
History and Philosophy of Science and Technology, 3 (2010) (http://www.rutherfordjournal.org/
article030108.html). ‘Bombe and Spider’ is an extract from what was known at Bletchley Park as
‘Prof ’s Book’, ‘Prof ’ being Turing’s nickname there (‘Mathematical theory of ENIGMA machine by A
M Turing’, NA HW25/3). Written by Turing in the summer or autumn of 1940, ‘Prof ’s Book’ served
as a training manual. It was not released into the public domain until 1996, and is available online in
The Turing Archive for the History of Computing at http://www.AlanTuring.net/profs_book. - Knox, Twinn, Welchman, and Turing, ‘Enigma – Position’ (Note 14); ‘Squadron-Leader Jones’
Section’, anon., GC & CS (c.1946), NA HW3/164, p. 1. - ‘Squadron-Leader Jones’ Section’ (Note 16), p. 1.
- ‘Squadron-Leader Jones’ Section’ (Note 16), p. 1.
- ‘Meeting held on 6th July 1950 to discuss “Bombes” ’, Birch, De Grey, Alexander, Fletcher, Foss,
Zambra, GCHQ, NA HW25/21. - ‘Squadron-Leader Jones’ Section’ (Note 16), p. 3.
- Information from Mavis Batey.
- ‘Squadron-Leader Jones’ Section’ (Note 16), pp. 3–4.
- 1676 women, to be precise: ‘Squadron-Leader Jones’ Section’ (Note 16), p. 14.
- Alan M. Turing (S. Turing 1959), p. 70.
- P. Hilton, ‘Living with Fish: breaking Tunny in the Newmanry and the Testery’, in Copeland et al.
(2006) p. 196. - W. G. Welchman, The Hut Six Story: Breaking the Enigma Codes, 2nd edn., M & M Baldwin (1997), p. 12.
- Letters from Peter Twinn to Copeland (28 January and 21 February 2001).
- ‘Staff and Establishment of G.C.C.S.’, NA HW3/82; letter from A. G. Denniston to T. J. Wilson of the
Foreign Office (3 September 1939), NA FO366/1059; Murray (Note 6),p. 42. - Letter from Twinn to Christopher Andrew (29 May 1981), quoted in C. W. Andrew, Secret Service: The
Making of the British Intelligence Community, Guild (1985), p. 453.