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. The Case of the Four Friends Despite the acclaim that An Oxford Tragedy had garnered, Masterman did not publish a follow-up until 1957. The novel, again starring Ernst Brendel, was called The Case of the Four Friends, which is "a diversion in pre-detection". In the novel, Brendel is persuaded by a group of friends to relate a story of how he "pre-constructed" a crime, rather than reconstructing it as in the conventional manner. As he says, "To work out the crime before it is committed, to foresee how it will be arranged, and then to prevent it! That's a triumph indeed, and is worth more than all the convictions in the world". His tale then was about four men, each of them either a potential victim or potential murderer. The pacing of the story is quite slow and the narrative is interrupted from time to time by discussion between Brendel and his listeners. Even so, the novel maintains its interest on the reader throughout, partly because of the originality of its approach. This novel was the last of his crime stories and he wrote no more works of fiction. However, his best known work was still to come, and it would involve his wartime experiences as part of the Twenty Committee. The Twenty Committee When World War II broke out, Masterman was drafted into the Intelligence Corps. After investigating and producing a report into the evacuation of Dunkirk, Masterman was appointed as a Civil Assistant in MI5. Within MI5 he was the chairman of the Twenty Committee, which was a group of British intelligence officials, including wartime amateurs, who held the key to the Double Cross System, which turned German spies into double agents working for the British. The committee's name was a pun based on the Roman numeral XX and its double-cross purpose. 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. It was Section B1(a) of MI5, established by Lt. Col. T. A. Robertson, who had the task of finding, turning and handling the agents themselves. Masterman became an Officer of the Order of the