The Ultra secret

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1. dalyNov 2018
   The Ultra Secret by F.W. Winterbotham
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2. chasilJul 2025
   "In his 1974 book The Ultra Secret, Group Captain F. W. Winterbotham asserted that the British government had advance warning of the attack from Ultra; intercepted German radio messages encrypted with the Enigma cipher machine and decoded by British cryptanalysts at Bletchley Park. He further claimed that Winston Churchill ordered that no defensive measures should be taken to protect Coventry, lest the Germans suspect that their cipher had been broken."

   https://en.wikipedia.org/wiki/Coventry_Blitz#Coventry_and_Ul...

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3. MattHeardMay 2014
   > In his 1974 book The Ultra Secret, Group Captain F. W. Winterbotham asserted that the British government had advance warning of the attack from Ultra: intercepted German radio messages encrypted with the Enigma cipher machine and decoded by British cryptoanalysts at Bletchley Park. He further claimed that Winston Churchill ordered that no defensive measures should be taken to protect Coventry, lest the Germans suspect that their cipher had been broken.[1] Winterbotham was a key figure for Ultra; he supervised the "Special Liaison Officers" who delivered Ultra material to field commanders.[2]

   > However, Winterbotham's claim has been rejected by other Ultra participants and by historians. They state that while Churchill was indeed aware that a major bombing raid would take place, no one knew what the target would be.[3][4]

   > Peter Calvocoressi was head of the Air Section at Bletchley Park, which translated and analysed all deciphered Luftwaffe messages. He wrote "Ultra never mentioned Coventry... Churchill, so far from pondering whether to save Coventry or safeguard Ultra, was under the impression that the raid was to be on London."[5]

   > Scientist R. V. Jones, who led the British side in the Battle of the Beams, wrote that "Enigma signals to the X-beam stations were not broken in time," and that he was unaware that Coventry was the intended target. Furthermore, a technical mistake caused jamming countermeasures to be ineffective. Jones also noted that Churchill returned to London that afternoon, which indicated that Churchill believed that London was the likely target for the raid.[6]

   Source: https://en.wikipedia.org/wiki/Coventry_Blitz#Coventry_and_Ul...

   References:

   1. Winterbotham, F. W. The Ultra Secret, London, Weidenfeld & Nicolson, 1974 ISBN 0-297-76832-8; also London, Futura, 1975, ISBN 0-86007-268-1

   2. Ray, John, "The Night Blitz", Cassel & Co 1996, ISBN 0-304-35676-X p. 155

   3. "Defending Coventry" (http://www.historiccoventry.co.uk/blitz/defend-cov.php). Historic Coventry.

   4. Hunt, David (28 August 1976), "The raid on Coventry", The Times: 11

   5. Calvocoressi, Peter (1981). Top Secret Ultra. New York: Ballantine Books. pp. 85–86. ISBN 0-345-30069-6.

   6. Jones, R. V. (1978). Most Secret War: British Scientific Intelligence 1939–1945. London: Hamilton. p. 149. ISBN 0-241-89746-7. This book was also published in the US under the title The Wizard War.

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