10 of History's Most Notorious Traitors

The Cambridge Five
Kim Philby jokes with newsmen at his mother's home during a 1955 press conference after being formally cleared of tipping off Guy Burgess and Donald Maclean that British intelligence was on to them. Philby later resigned from MI6, but agents interrogated him about this again in 1963. As they closed in, he escaped to Russia. © Bettmann/CORBIS

A womanizer who married four times. A flamboyant gay man with a penchant for drunkenness. A famous art historian knighted by Queen Elizabeth II. It may sound like the lineup for a new HBO miniseries, but these men were real-life spies during World War II and beyond. Along with two fellow Cambridge University graduates, they penetrated British intelligence agencies and turned over secrets to the Soviets.

The Cambridge Five -- Harold "Kim" Philby, Donald Maclean, Guy Burgess, Anthony Blunt and John Cairncross -- were members of the British elite and so ensconced in their communist beliefs they refused payment for their spy work.

All were hired to work in key British intelligence positions and continually alerted Moscow about British and U.S. plans, including efforts to construct an atomic bomb in 1941 and Korean War strategy, causing the deaths of many. Things started unraveling when Americans deciphered a coded Soviet message that implicated Maclean. Philby warned him, and in 1951 Maclean and the flamboyant Burgess promptly defected to Russia -- a move that left the remaining spies under a low-hanging cloud of suspicion.

Philby and Cairncross were investigated by MI6, the British foreign intelligence service, but not charged. Nevertheless, both were forced to resign. Cairncross moved to France while Philby escaped to Russia in 1963. Blunt confessed and was granted immunity to remain in England. He was stripped of his knighthood when Prime Minister Margaret Thatcher publicly revealed his espionage in 1979. Maclean, Philby (who had an affair with Maclean's wife) and Burgess all lived in Moscow until their deaths, nostalgic for England. None of the five were ever charged with any crimes [sources: Boghardt,Barnes].