Other Soviet spies were to defect later but Gouzenko was perhaps the most important because of the shocking impact he made on a complacent West.

ECONOMIST: Svetlana Gouzenko

Alger Hiss and Julius Rosenberg were Soviet spies.

ECONOMIST: History of espionage: Dark secrets | The

In 1969, Gerald Brook was released to Britain by the Soviet Union in exchange for spies Peter and Helen Kroger.

CNN: Thursday,

The Soviet Union was always looking for apprentice spies, and Miss Werner seemed a promising candidate.

ECONOMIST: Ruth Werner, Soviet spy, died on July 7th, aged 93

The diaries, made available online from the National Archives on Friday, cover the period when evidence emerged of the treachery within the British establishment in the form of the men - who would become known as the Cambridge Spies - who had spied for the Soviet Union.

BBC: Cambridge Spies: MI5 diaries revealed

As a protector of the state Vladimir Semichastny was the master of the Soviet Union's vast and effective worldwide network of spies.

ECONOMIST: Vladimir Semichastny

In 1945, the defection of Igor Gouzenko, a code clerk at the Soviet embassy in Ottawa, and Elizabeth Bently, an American courier between the spies and the Soviets, plus the knowledge that at least some of their secret cables had been decoded, led to an almost total shut-down of the espionage apparatus in the United States.

ECONOMIST: History of espionage: Dark secrets | The