SAS fears barrage of revelations: A best-seller could lead to undercover secrets being exposed. Christopher Bellamy reports

DETAILS OF covert SAS operations never acknowledged by the Government could be made public, senior military sources fear.

Their concern comes in the wake of the highly successful book Bravo Two Zero by a former SAS sergeant using the pseudonym Andy McNab, which has sold 300,000 copies since it was published last October. A paperback version is to be published in September and the BBC has bought the film and television rights.

McNab was part of an eight-man team sent behind enemy lines during the Gulf war to destroy Scud missile sites. They were taken prisoner and tortured by Iraqis. Five members survived and were released; three died. The other four survivors are understood to be still serving. McNab's account of his experiences, with some passages removed, was cleared by the Ministry of Defence, which could have prevented publication.

The Director of Special Forces is understood to be concerned that more books will follow. But the concern is probably less to do with the minutiae of SAS techniques than with ex-soldiers writing about operations in places where they were not supposed to be.

Military sources said that many people in the Army's SAS and the Royal Marines' SBS had interesting stories to tell about operations 'on five continents'. But Britain has not admitted fighting wars on five continents in recent years, although it is probable that Special Forces have been deployed in areas not admitted to by the Government - possibly in South America against drug barons, in Africa and the former Soviet Union.

The involvement of the SAS in the UN operation in Bosnia, though long suspected, only became apparent in April when an SAS man was killed in Gorazde. There have also been proposals to increase the size of the SAS but most of its officers oppose dilution of the elite force.

Sources in the publishing world said they were unaware of a wave of further books on SAS operations. But the concern of the SAS high command - known as the 'Head shed' - that other books might appear which had not been through the MoD's clearance procedure, is understandable.

One source close to the regiment said: 'There is a groundswell of feeling that McNab has gone too far in revealing the nitty-gritty.' However, others said his book was seen as great publicity for the SAS, that he was considered a hero, and that former colleagues regarded him with affection and admiration, though some jealousy was inevitable.

The SAS was little known until its dramatic intervention in the Iranian Embassy siege in April 1980. Its participation in the 1982 Falklands war was well publicised - since then a number of revealing books have been written, but mostly by senior officers.

The concern is that publication of a book by a former sergeant might have opened the floodgates. Even with special SAS pay, and taking into account allowances for technical skills, an SAS soldier or non-commissioned officer is unlikely to earn more than about pounds 16,000 a year. Once the advances payable on a book became known, there was a risk the secretive regiment could start to 'leak like a sieve', the military sources said.