After he reached Britain, Blake joined the
Royal Navy as a
sub-lieutenant before being recruited by the Secret Intelligence Service (MI6) in 1944. For the rest of the war, Blake was employed in the Dutch Section. He intended to marry an MI6 secretary,
Iris Peake, but her family prevented the marriage because of Blake's Jewish background and the relationship ended. He was posted thereafter to the British
legation in
Seoul, South Korea, under
Vyvyan Holt, arriving on 6 November 1948. Under cover as a vice-consul, Blake's mission was to gather intelligence on Communist
North Korea, Communist
China, and the
Soviet Far East. The
Korean War broke out on 25 June 1950, and Seoul was quickly captured by the advancing
Korean People's Army of the North. After British forces joined the
United Nations Command defending the South, Blake and the other British diplomats were taken prisoner. As the tide of the war turned, Blake and the others were taken north, first to
Pyongyang and then to the
Yalu River. After seeing the
bombing of North Korea, and after reading the works of Karl Marx and others during his three-year detention, he became a communist. At a secret meeting arranged with his guards, he volunteered to work for the Soviet Union's spy service, the
MGB. In an interview, Blake was once asked: "Is there one incident that triggered your decision to effectively change sides?" Blake responded, In his first interview, in 1990, with
Tom Bower for 'The Confession', a BBC TV documentary, Blake said that he had been tempted towards communism during his Russian course in Cambridge while serving with MI6, and had been finally convinced while reading
Karl Marx's
Das Kapital during his imprisonment in North Korea. Following his release in 1953, Blake returned to Britain as a hero, landing at
RAF Abingdon. In October 1954, he married MI6 secretary Gillian Allan in St Mark's Church (North Audley Street) in London. In 1955, he was sent by MI6 to work as a
case officer in
Berlin, where his task was to recruit
Soviet officers as double agents. Blake informed his KGB contacts of the details of British and American operations, including
Operation Gold in which a tunnel into
East Berlin was used to
tap telephone lines used by the Soviet military, and the similar
Operation Silver by the British in Vienna. He was called
Agent Diomid. To protect Blake from exposure, the Soviets decided not to "discover" the tunnel until it had been in operation for nearly a year. Over nine years, Blake is said to have betrayed details of some forty MI6 agents to the KGB, destroying most of MI6's operations in
Eastern Europe, although this remains unsubstantiated. Blake later said of this, "I don't know what I handed over because it was so much". Although Blake's espionage during the Cold War is famous and has regularly been pored over, it has been in a less detailed way than the
Cambridge Five spy ring, because "Blake was never part of this [elite] class-ridden inner circle", according to an article by
The Guardian after Blake's death. "Born in Rotterdam to a Dutch mother and an Egyptian Jewish father [he] was never considered one of them". ==Discovery and conviction==