[drpix]

How much can we rely on the fact that British Intelligence was "unimpressed by Washington's claims of communist links?" They go back to a time when that agency was infiltrated at its highest levels by Stalin's "Cambridge Five." This ring of spies actually running large parts of British Intelligence included Philby, Maclean & Burgess.

Britain's political leaders were so bamboozled that their Foreign Secy personally attested to Philby's loyalty - years after Maclean and Burgess had fled into hiding (to later defect to the USSR) - allowing Philby to survive for years before imminent detection also caused him to also defect to the USSR.

"Victim of McCarthyism?" McCarthy may have been a flawed messenger, but his messenger was vindicated by history.

[Focault's Pendulum]

The Cambridge Five was a ring of spies, recruited in part by Russian talent spotter Arnold Deutsch in the United Kingdom, who passed information to the Soviet Union during World War II and at least into the early 1950s. Four members of the ring have been identified:
Kim Philby (cryptonym: Stanley),
Donald Duart Maclean (cryptonym: Homer),
Guy Burgess (cryptonym: Hicks)
and Anthony Blunt (cryptonym: Johnson);
jointly they are known as the Cambridge Four.

Several people have been suspected of being the "fifth man" of the group; John Cairncross (cryptonym: Liszt) was identified as such by Oleg Gordievsky

Cairncross eventually confesed as did Blunt, however long after his retirement.

There were more than just the identified five in this ring, probably eight maybe as much as ten.

One special note:

John LaCarre's novel Tinker Tailor Soldier Spy was very loosely based not only on This espionage ring, but the author was the first person to use the term "mole ".