Sir Maurice Oldfield, a former director-general of MI 6, the British intelligene service, died Tuesday in a hospital, the government announced. Its location and other details were not made available. Press reports said he had cancer.

Sir Maurice headed MI 6 from 1966 to 1978. By tradition, the identity of the holder of that position is kept secret.Officially, his job was classified as a regular Foreign Office post. But in 1973, a German magazine printed a photograph of him and years later an American newspaper named him as head of the service. British editors said they knew who he was but were forbidden by law from publishing anything about him.

Shortly after his retirement, Sir Maurice was called back to duty to coordinate security operations against terrorists in Northern Ireland. He served as a liaison between the army, the police and the British government. He retired again last year for reasons of health. He settled in Derbyshire in northern England.

Sir Maurice, a round-faced man with large spectacles, once was described by Kim Philby, a Soviet spy who successfully fled to the Soviet Union in the 1960s, as "formidable."

Sir Maurice became an intelligence officer in the Middle East during World War II. Later, he was attached to the Foreign Office. He was commissioner general of Singapore from 1950 to 1952 and counsellor at the British Embassy in Washington from 1960 to 1964. It was reported that his duties included regular contact with the CIA and the FBI.

There has been some speculation that Sir Maurice formed the basis of "M", the fictional spy chief of Ian Fleming's James Bond novels. Fleming, who died several years ago, never admitted this. ("M" was a retired admiral, not a civil servant.) Others have said that he was the basis for George Smiley, John Le Carre's fictional master spy. In 1979, Le Carre said in an interview that he had met Sir Maurice, but that this was "long after Smiley was born."

Sir Maurice, a bachelor, enjoyed gardening, playing the organ, and classical music.