The man described by those in the know as one of the most able agent handlers in the history of the KGB is now a rosy-cheeked pensioner with a white goatee and an infectious laugh.


Yury Ivanovich Modin looks more like a twinkle-eyed grandfather than a 44-year veteran of the Soviet secret service who ran what historians say was the century's most successful spy ring.


The much-decorated Colonel Modin's memoir of the British spies whose secrets he collected, translated, evaluated and passed to Moscow has just been published in London under the title "My Five Cambridge Friends."


Modin, interviewed in his Moscow flat a few minute' walk from the city zoo, said that despite a sentimental desire to revisit old haunts in London for the first time since 1958 he would not be there to launch his book.


Britain might have an old score or two to settle with Modin, who at the height of his agent-running career in the late 1940s was sending top secret British government papers to the Kremlin on an almost daily basis.


But Modin can afford to be generous. "I have a very high opinion of British intelligence," he said.


He described his book as "neither a book of memoirs nor a detective thriller; it's an attempt to give a psychological portrait of these five men."


Of the five Cambridge graduates, all communists, all but one is now dead. Their spying careers efectively ended in 1951, with the spectacular flight to Moscow of diplomats Donald Maclean and Guy Burgess.


Kim Philby died in Moscow in 1988, 25 years after Burgess and five after Maclean. Art historian Anthony Blunt, named as the "fourth man" by prime minister Margaret Thatcher in 1979, died disgraced but a free man in Britain in 1983.


Only John Cairncross, the least known of the five, is still alive, living in France. Modin confirms for the first time that the information supplied by the shadowy Cairncross, including Moscow's first news of the Anglo-American atomic bomb project, was every bit as important as that given by the other four.


Modin's book, written largely from memory, gives a vivid account of the almost sexual intensity of brief clandestine encounters with his agents. "In that half hour one gets more than out of spending a whole month with someone else," he said. After these meetings, Modin would go to a pub for a glass of beer to settle his nerves.


In Moscow, Modin befriended the deeply unhappy and homesick Burgess in the years until he died, largely of drink, in 1963.


Modin went on to become a top professor at the KGB's Andropov academy, lecturing generations of young Soviet intelligence officers on how to spy and, more importantly, how not to get caught.


Though officially retired since 1988, he hints there is still demand for his skills on a part-time basis in the new post-Soviet Russia.


With a disarming grin, he confesses, "I still give the occasional private lesson, now and again."