Since World War II, we've been inundated with spy novels, movies and TV series, but "Philby, Burgess and Maclean" (Channel 5, 8:30 p.m.) is an excellent and unusual footnote to the genre, for all that.

Its real message is that although Soviet intelligence recruited badly at England's Cambridge in the early 1930s, the KGB's forerunners knew the British Establishment so well it didn't matter a bit.

This low-budget entry in the Mobil "Summershow" series is a little short on the overly familiar atmospherics of espionage, maybe, but the superb cast won't give you a chance to miss them.

It focuses instead on the period after 1945, well after the barn door to America's atomic secrets had been locked, and on the unpleasant (and unraveling) personalities of the three onetime Cambridge sexual partners who stole those secrets for the Soviets from fairly exalted positions in the British Foreign Office.

The program ends as the trio runs off to Moscow -- where Kim Philby has only recently won another row of Soviet ribbons for his dedication to the cause of world peace.

Philby (played by Anthony Bates) was the leader of the sorry trio. His position at Whitehall protected the "dirty, dissolute" Guy Burgess (played by "I, Claudius" star Derek Jacobi) and the drunken wreck Donald Maclean (Michael Culver) even as the British, prodded by our suspicious FBI, dithered in later years over what to do with them.

"But they're out sort of people," protests a high Foreign Office official, as the evidence against the three mounts up. That kind of Old School Tie sappiness, bolstered by the breed's sense of fair play, saved all three from the high jump. Relations between U.S. and British intelligence circles since their defections have never been quite the same either.

They were a remarkably unhappy lot. Two of them were caught in unfriendly marriages with wives who suspected their homosexuality. Their youthful communist ideals had been battered by years of Stalin and their lives as agents. They drank too much; each, in his own way, was going to pieces under the pressures.

Earlier this year, it was revealed that Sir Anthony Blunt, the Queen's own art expert, was the mysterious "fourth man" who recruited the trio at Cambridge. His absence from the 1978 film is noted by host James Earl Jones at the start of tonight's program. But that doesn't matter, either. Blunt's flawed handiwork is inferred in every scene and with every nervous tic of his melancholy charges. Incidentally, this is occasionally pretty strong stuff, and parents should be warned.