British on trail of another Soviet mole?

Persuasive evidence that one of Britain's leading "spycatchers" worked for the Kremlin throughout most of the cold war has been placed before Prime Minister Margaret Thatcher.

Whitehall insiders are calling it the clearest indication so far that post World War II British intelligence was not just penetrated, but dominated, by the KGB. A huge range of the West's most vital secrets may have passed to Moscow on an almost routine basis.

The man named is the late Sir Roger Hollis, director general of the security service, M15, from 1956 to 1965. In a book by a leading investigative journalist, Chapman Pincher, Sir Roger is pinpointed as the likely protector of such notorious spies as Kim Philby, Guy Burgess, Donald Maclean, George Blake, and Anthony Blunt.

Professor Blunt's role as a Soviet agent was revealed Last year. He had been an art adviser to Buckingham Palace, but it emerged that he was recruited by the Russians at Cambridge University before the war.

Allegations against Sir Roger, which Mr. Pincher says are based on the firm belief of many of his former colleagues that he was a top Soviet agent, will be the subject of a special House of Commons statement by Prime Minister Margaret Thatcher at the end of the week.

The absence of an immediate, categorical official denial of the allegations is being taken as a sign that there is considerable substance to Mr. Picher's revelations.

Like so many other Britons whose work for Russia has been uncovered, Sir Roger Hollis was a pillar of the establishment. Former colleagues remember him as efficient, affable, and relaxed. He had a first-rate mind and was recruited to British intelligence as a result of friendships and contacts made at Oxford University before the war.

His Oxford background is a little unusual --tablishment went to Cambridge University. Sir Roger's father was the Anglican Bishop of Taunton.

Mr. Picher's case against Sir Roger is that soon after his retirement, he was subjected to nonstop 48-hour questioning by British intelligence. He was asked if he had been responsible for a series of damaging intelligence leaks. Apparently he could not supply convincing replies.

The interrogation did not produce enough evidence to lay charges against Sir Roger.

Later, after Sir Roger's death, a former secretary of the Cabinet, Lord Trend , was called out of retirement to carry out further inquiries. Whitehall sources are saying that Lord Trend concluded that Sir Roger had indeed been a KGB agent, but that the evidence was circumstantial.

These reports make it essential for Mrs. Thatcher to give Parliament a detailed account for what is officially known about Hollis and his alleged spying activities. Meanwhile, members of his family say they simply cannot believe the allegations.

The main significance of the Hollis affair is that it gives strong support to a theory held by many intelligence experts on both sides of the Atlantic -- that there were highly placed moles in British intelligence who were never caught and who made the work of Mr. Philby and other notorious spies possible.

Mr. Pincher has written about British intelligence for many years and is utterly convinced that M15 and its sister body M16 were riddled with Soviet spies.

According to one private Whitehall assessment, if the charges against Sir Roger are true, the Russians from 1945 onward had working for them a man with the highest security clearance who had access to most of the top British and US secrets.

Sir Roger saw the minutes of Cabinet committees dealing with security and intelligence as well as secret reports of British and American agents around the world. Mr. Pincher says he appeared determined to block attempts to uncover the source of security leaks during his term in office.

Immediately after Sir Roger retired, Mr. Pincher says, most of the leaks stopped.

Although they are reluctant to say so before Mrs. Thatcher makes her Commons statement, members of Britains intelligence hierarchy are not surprised by the weight of evidence Mr. Pincher piles up in support of the case against Hollis.

These people include the officials and former senior British intelligence officers still alive who worked for the Russians, but that most of them are retired. "As far as I can tell, the service is clean today," he said.