Notes
1. TNA: PRO (The National Archives: Public Record Office, Kew): HW 25/16: Mayer, S. “The breakinq up of the German ciphering machine ‘ENIGMA’ by the cryptological section in the 2nd department of the General Staff of the Polish Armed Forces”. Colonel Stefan Mayer was the pre-war head of the intelligence section of the 2nd department; Ciechanowski, “Literature on the activities of Polish intelligence”, 32.
2. Kahn, Seizing the Enigma.
3. Sebag-Montefiore, Enigma.
4. Hinsley, British Intelligence in the Second World War, 956.
5. Welchman, The Hut Six Story, 164–165.