His highest-profile role was as Vice-Chancellor of the University of Oxford, but he was also well known as chairman of the Twenty Committee, which during the Second World War ran the Double-Cross System, controlling double agents in Britain.

He served as Watson to the novel's Sherlock Holmes, an amateur sleuth named Ernst Brendel, a Viennese lawyer "of European reputation".

While it was a variation of the old theme of evil deeds done in a tranquil setting, it did establish the tradition of Oxford-based crime fiction, notably in the works of Michael Innes and Edmund Crispin.

Strictly speaking, the committee was responsible for providing information for the agents to be transmitted to the Abwehr and other German intelligence agencies, deceiving them of Allied intentions and war plans.

In November 1945 at the Savoy Hotel in London, Masterman and a select few of B1 (a) section were awarded the Order of the Yugoslav Crown by the exiled King Peter II.

[3] It is widely assumed that the writer Ian Fleming, himself involved in wartime intelligence, adapted Masterman's name for the (female) character of Jill Masterson in his James Bond novel Goldfinger (1959).

[6] In April 1970, when the government again refused, he decided to have it published in the United States, where he felt he would be out of reach of the Official Secrets Act.

Pearson was more than happy to help Masterman because he also served in the Twenty Committee (though not a member) as the wartime head of the counterintelligence division of the Office of Strategic Services.

Yale had contributed many scholars and students to the OSS, and Chester B. Kerr, director of the press, saw the importance of the book historically and commercially.

For a time British authorities threatened Masterman with legal action, but in the end bowed to the inevitable and allowed publication, with the proviso that sixty passages in the manuscript be deleted.

The book, The Double-Cross System in the War of 1939–45, was finally published in February 1972, with a foreword by Pearson, who guardedly did not refer to his work in the committee.