1. The history of British communications security is an especially important area that has long been neglected. For a path-breaking essay on cipher and document security see, D. Dilks, ‘Flashes of Intelligence: The Foreign Office, The SIS and Security Before the Second World War’, in C. Andrew and D. Dilks (eds), The Missing Dimension: Governments and Intelligence Communities in the Twentieth Century (London: Macmillan, 1982), pp. 101–25.
2. More recently see J. Ferris, ‘The British “Enigma”: Britain, Signals Security and Cipher Machines, 1906–1946’, Defense Analysis, 3, 2 (1987), pp. 153–63 and also
3. R.A Ratcliff, Delusions of Intelligence: Enigma, Ultra, and the End of Secure Ciphers (Cambridge, Cambridge University Press, 2006).
4. R.J. Aldrich, ‘The Ultimate Spy: Why the Real James Bond is a Supercomputer’, BBC Science Magazine, 248 (November 2012), pp. 55–9.
5. See for example Matthew Aid, Secret Sentry: The Top Secret History of the National Security Agency (New York: Bloomsbury 2009);