F . W . Winterbotham Frederick William Winterbotham ( 1897 – 1990 ) was a British Royal Air Force officer ( latterly a Group Captain ) who during World War II supervised the distribution of Ultra intelligence . His book " The Ultra Secret " was the first popular account of " Ultra " to be published in Britain . World War I service . Born in Stroud , Gloucestershire Winterbotham enlisted in the Royal Gloucestershire Hussars Yeomanry at the start of the war . He later transferred to the Royal Flying Corps , and became a fighter pilot . He was shot down and captured on 13 July 1917 , and spent the rest of the war as a PoW , for much of the time in Holzminden . Between the wars . Winterbotham took a law degree , but had no liking for an office job . He pursued farming opportunities in Britain , Kenya , and Rhodesia without success . By 1929 he was back in Britain , and considered becoming a stockbroker in the City . Instead he was recruited to join the staff of the Royal Air Force , where he was assigned to the newly created Air Section of the Secret Intelligence Service ( MI - 6 ) . During the next few years , Winterbotham began the process of building up an intelligence service for the RAF . His job was to gather information on the development of military aviation in hostile or potentially hostile countries . He recruited agents , and filed and analyzed their reports . One of these reports revealed that Germany had secret arrangements with the Soviet Union for the training of military pilots in violation of the Treaty of Versailles . William de Ropp , the agent who supplied this information also informed Winterbotham that the Nazis , not yet in power , wanted to cultivate high - level contacts in Britain ; they imagined that " imperialist " Britain would be sympathetic to their own dreams of racial conquest . Winterbotham , who was socially well - connected , seemed a likely channel . This led to a visit by Nazi " philosopher " Alfred Rosenberg in 1932 . Winterbotham , with the full knowledge of MI - 6 , escorted Rosenberg around Britain , made some appropriate introductions , and played up to him . Neither Ropp nor Rosenberg knew that Winterbotham had any intelligence connections - he was just a civilian official of the Air Staff . Winterbotham continued in this role for the next seven years . He became a regular visitor to Germany , and an apparent Nazi sympathizer . As such , he was welcomed into the highest circles in Germany , meeting with Hitler and Göring , and with Goering ' s Luftwaffe subordinates such as Erhard Milch and Albert von Kesselring . He gathered a tremendous amount of information on the Luftwaffe and on German political and military intentions . In 1938 , Winterbotham recruited Sidney Cotton to carry out some very successful aerial reconnaissance over Italy and Germany in 1939 - 40 in a private Lockheed 12A aircraft . Ultra . These games came to an end when World War II broke out in 1939 . As a top ranking member of MI - 6 ( he reported directly to its head , Sir Hugh Sinclair , and his successor in 1940 , Sir Stewart Menzies ) , Winterbotham was fully aware of Britain ' s successful code - breaking operation against the German Enigma cipher machine . The intelligence derived from Enigma decrypts was absolutely authentic ( it was what the Germans were telling each other ) and it was often of immense value . This source was so valuable it was given the special classification " Top Secret Ultra " , or simply " Ultra " . But at first the British forces did not know what to do with the information . This problem was solved during the later part of 1940 , as teams of analysts were formed to scan , digest , and file the messages , and channels were established for forwarding key messages to the appropriate field commands . A key part of the solution was arranging for the secure delivery of " Ultra " to the various commanders , and making sure that they did nothing to give away the secret that Enigma was being read . Winterbotham took charge of this process . He formed " Special Liaison Units " , which were attached to each field headquarters that received Enigma . An SLU consisted of a few RAF officers and enlisted men , low in rank to avoid drawing attention . They received " Ultra " messages by radio from Britain , carefully encrypted in Britain ' s strongest cipher . They decrypted the messages , and handed them over to the commander , who was often the only person cleared to know where the information came from . ( At some HQs , there might be one or two deputies also cleared . ) The SLU was expected to retrieve the " Ultra " message after the commander had read it and keep it under lock and key . The SLU was also expected to keep the recipient commander from telling anyone else about the origins of the message or acting too obviously on its contents . Naturally , this sometimes led to conflicts with field commanders who objected to being second - guessed . After the U . S . entered the war , these field commanders were often not British . Winterbotham was responsible for recruiting and training the SLU personnel for this difficult role . They had to be very able technically , be close - mouthed , keep a low profile , and also be diplomatic enough to manage commanders who far outranked them . When diplomacy failed , Winterbotham flew out to the problem HQ to resolve the quarrel . He had the ultimate authority of the Allied governments behind him , as both Britain and the U . S . would do almost anything to avoid exposing the secret of the decryptions . Winterbotham succeeded brilliantly all around . The SLU personnel he picked did splendid jobs ; and he was very effective in dealing with recalcitrant commanders . There were no leaks about " Ultra " in the field . " The Ultra Secret " . " Ultra " remained strictly secret even after the war . Then in 1974 , Winterbotham ' s book , " The Ultra Secret " , was published . This was the first book in English about " Ultra " , and it explained what " Ultra " was , and revealed Winterbotham ' s role , particularly with regard to the dissemination and use of " Ultra " . There had been mentions of Enigma decryption in earlier books by Władysław Kozaczuk , Ladislas Farago , and Gustave Bertrand . However , Winterbotham ' s book was the first extensive account of the uses to which the massive volumes of Enigma - derived intelligence were put to by the Allies , on the western and eastern European fronts , in the Mediterranean , North Africa , and perhaps most crucially , in the Battle of the Atlantic . Winterbotham ' s account has been criticized for inaccuracies and self - aggrandizement . Winterbotham was evidently no cryptologist and had only slight understanding of the cryptologic side of the multi - faceted and strictly compartmentalized " Ultra " operation . His description of the pioneering work done by Poland ' s Cipher Bureau before the war is minimal and incorrect . Winterbotham later responded that he had simply passed on the story that he had been given at the time . He erroneously suggested that Japan ' s PURPLE cipher machine was a version of the German Enigma and confused " Dilly " Knox with a different person . Perhaps the worst flaw in the book is the myth of Winston Churchill and the Coventry Blitz . During The Blitz of 1940 – 1941 , Coventry , a British industrial city , was severely bombed by the Luftwaffe on the night of 14 – 15 November . There was heavy damage and numerous civilian casualties . Winterbotham asserted that Enigma decrypts had provided clear advance warning of the raid but that Churchill personally decided not to take any special countermeasures that might alert the Germans that the British were reading Enigma . This story has been widely repeated , even though it has been thoroughly refuted by other historians and memoirists . Peter Calvocoressi was head of the Air Section at Bletchley Park that 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 . " Nevertheless , Winterbotham ' s book is a vivid first - hand account by one of the key figures in the " Ultra " story , and much of the book still retains interest and validity . Winterbotham ' s conclusion was 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 " . " Other books . Before and after " The Ultra Secret " , Winterbotham wrote several other books dealing with various aspects of his intelligence work .