The infamous foursome of Guy Burgess, Kim Philby, Donald Meclean and lastly Anthony Blunt. Recruited from Cambridge in 1930 were double agents spying first for MI5 then turning to spy for the Russians.

The information that they would pass on to the Russians would alter the balance of power from Britain and America to the Soviets and it would have a powerful effect on the Cold War that followed culminating in the Nuclear standoff between Khrushchev and Kennedy in the Cuba crisis.

However his biggest service to the KGB (Russian Intelligence) at this time was to get Kim Philby into his section, helping launch Philby's career as a KGB agent. In 1944 Burgess joined the Foreign Office news department, and was later posted to Washington.

He arrived in the US and moved in with Philby who had been appointed British liaison officer with the CIA and FBI. This was a breach of a KGB ban on agents living together but he argued that he would be able to keep an eye on Burgess and curb his drunken behaviour.

 In 1951 the KGB sent Burgess back to London to tell Maclean he was about to be interrogated as a suspected Soviet agent, and to arrange Maclean's escape to Moscow.

When Burgess failed to return to America, the association he had with Philby meant that Burgess came under suspicion of being a spy.  He was officially cleared, but his career as a KGB agent was over and he never forgave his erstwhile friend.

In 1963 Russia jailed a British 'spy' British businessman Greville Wynne, aged 44 he was accused with Soviet scientific official Oleg Penkovsky aged 43 of spying for MI6

Wynne would serve three years in prison and five in a labour camp but Penkovsky was given the death sentence. He was also stripped of his rank of colonel and all his medals.  During the four-day trial, the court heard both men had spied for British and American intelligence. Most of the evidence based on confessions given by the two men.

Colonel Oleg Pentovsky spied for MI6 during the cold war he was what is called a "Double agent" firstly spying for his own country then being “Turned” by the agencies of the countries he was spying on to spy for them.