The Ultra Secret (Hardback)
Guarding the Secrets that Won the Second World War

Pages: 200
Illustrations: 16 mono illustrations
ISBN: 9781036135294
Published: 31st August 2025
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In April 1940, when British cryptographers at Bletchley Park decrypted some German air force messages, Group Captain Frederick Winterbotham recognized the potential of such intelligence and established a secure system to handle it. He created Special Liaison Units, small teams of RAF officers and enlisted men, to receive and securely distribute decrypted Ultra messages to relevant commanders. These messages, transmitted through encrypted radio signals, were kept highly classified, with recipients unaware of their origins.
Winterbotham's units played a critical role in key moments during the war. His selected intercepts provided early insights into the French collapse during the Battle of France and proved crucial in the Battle of Britain, North Africa, El Alamein, and the D-Day invasion. The Ultra intelligence was vital for informing Allied military decisions, with Winston Churchill receiving urgent messages directly via a secure phone line.
By 1944, the system was highly efficient, delivering time-sensitive information, such as the rapid intelligence on the German evacuation of the Casino line in Italy. Winterbotham also analyzed the surprise of the 1944-45 Ardennes Offensive, noting that the absence of German signals should have raised alarms.
Winterbotham’s first-hand account of the Enigma program offers an unmatched perspective on its strategic importance.
Rating: 5 out of 5 stars
NetGalley, Sandra Miller
This book by Group Captain Winterbotham was first published in 1974 and provided the detail of how the highly classified decrypted signals sent by the Germans during WWII and dubbed Top Secret Ultra or just Ultra, were used. Even after 50 years the book reveals to modern generations the details of some of the highly publicised battles of that conflict were orchestrated by the Allies, in such a way that the enemy did not realise that their codes had been broken.
Much has been written and filmed about the code breakers of Bletchley Park but this book takes us to the employment and application of the Ultra signals and message content.
Winterbotham concludes that the War's outcome "was, in fact, a very narrow shave, and the reader may like to ponder [...] whether or not we might have won had we not had Ultra"
A fascinating book that enhances our understanding of the major operations conducted during WWII and of the man who was responsible for managing the Ultra information.
About Gp Capt Frederick William Winterbotham CBE
Born on 16 April 1897, Frederick William Winterbotham was educated at Oxford University. In the First World War he transferred to the Royal Flying Corps, but was shot down over the Western Front in 1917, spending the rest of the war in captivity. Early in 1930, Winterbotham joined the Air Staff and was officially assigned a role as a liaison officer; unofficially he served in the Air Department of the British Secret Service. On the outbreak of the Second World War, he established a new organisation for the translation, distribution and security of Ultra at Bletchley Park. In 1943 he was awarded the CBE, and attained the rank of Group Captain. He died of natural causes on 28 January 1990, aged 92.
About Sir John Slessor GCB, DSO, MC, DL
Marshal of the Royal Air Force