Frederick William Winterbotham CBE (16 April 1897 – 28 January 1990) was a British Royal Air Force officer (latterly a Group Captain) who during World War II supervised the distribution of Ultra intelligence.

He was born in Stroud, Gloucestershire, the younger child and only son of Frederick Winterbotham, solicitor, and his wife, Florence Vernon Graham.

He was shot down and captured on 13 July 1917, after a dogfight in the Passendale area by a member of the Luftstreitkräfte squadron known as Jagdstaffel 11 which produced many high-scoring "aces".

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.

A report written by a William Winterbotham, dated 16 February 1937, filed in AIR 40/224, provides highly technical analysis of events that reflected his professional military experience.

[6] 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.

In April 1940 the cryptographers at Bletchley Park made a breakthrough when they succeeded in deciphering four small messages regarding Luftwaffe personnel.

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.

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 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 acknowledged in the book that he was no cryptologist, had only slight understanding of the cryptologic side of the multi-faceted and strictly compartmentalized Ultra operation, and had no access to official records so was written from memory.

He erroneously suggested that Japan's PURPLE cipher machine was a version of the German Enigma and confused "Dilly" Knox with a different person.

[citation needed] Peter Calvocoressi was head of the Air Section at Bletchley Park that translated and analysed all decrypted Luftwaffe messages.

"[9] Winterbotham concluded 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".

Portal overrode the resistance of Sir Arthur Harris, head of Bomber Command, to Wallis' proposal, and the Dambusters raid, code-named Operation Chastise in May 1943, was approved.