Colonel Goleniewski’s debriefing in London at the end of 1960, which enabled the security services to identify the Portland spy ring, also led to the identification of George Blake as the KGB’s agent within MI6.

Sir Dick White, the head of MI6, was incensed. He was determined to show no mercy in Blake’s case, despite a then recent tendency not to prosecute if the offender turned Queen’s evidence (i.e. told everything he knew about Soviet strategies and about his Soviet contacts). Prime Minister Harold Macmillan was informed. He wanted the whole thing to be hushed up because of the embarrassment it would cause, particularly with the Americans. White, however, stood firm and insisted upon prosecution.

MI6’s embarrassment increased when they looked again at Blake’s personal file. As with Philby, hindsight showed that he should probably not have been allowed to work for MI6 or, at least, should not have been allowed to continue after his return from Korea.* His father was only a naturalised British subject; his mother was not British; and he had spent his formative years in Egypt, close to an uncle and cousins who were declared Communists.

While none of this in itself precluded Blake from being invited to join MI6 then, surely, his experience in Korea should have raised a warning flag. The North Koreans had kept him prisoner for close to three years, and they had acquired a strong reputation, in part fictitious, for ideological re-education, brainwashing and even mind control.

It was perhaps incongruous that Philby, who had been put out to pasture owing to the continuing rumours about his loyalty, was at that time in Beirut in the guise of a correspondent for The Economist. Beirut was close to MECAS and he would probably have visited the organisation from time to time. Neither Blake nor Philby knew that the other was also a Soviet spy, though Blake would have reached his own conclusions about Philby in the light of the press reports and, no doubt, internal office gossip.

There was, as yet, little hard evidence of Blake’s espionage activities. He was in a foreign country and still had a few months of his Arabic course to complete, so it would be difficult to recall him to the UK immediately without raising some misgivings. Sir Dick decided simply to send a message to him through Nicholas Elliott, the head of the MI6 station in Beirut, saying that he was required in London for consultations. No dates were given, so there appeared to be no hurry. Blake told his wife and colleagues it was either for news of his next posting, word of a promotion, or both.

He returned to the UK by air on 3 April 1961, which was Easter Monday – a national holiday – so he was able to stay with his mother prior to reporting to MI6’s Broadway headquarters the next day.

He was taken straight up to the chief’s office where White and two interrogators – Terence Lecky and Harold Shergold – were waiting for him.

Throughout the morning Blake denied their accusations of treason and espionage. At lunchtime he left the building by himself, took a circuitous route to a red public telephone booth, pulled the heavily sprung door open, and hesitated for a long moment before finally deciding not to dial the emergency number he had been given by his Soviet master.

Back in White’s office after lunch he continued to deny the charges until Shergold asked him why he had not called his Soviet contact during the lunch break. This seemed to unnerve Blake, who had not realised he was under surveillance throughout the lunch break. Slowly, he allowed himself to acknowledge that he had spied and then, bit by bit, he confessed to everything. Between the confessions he put up a textbook defence of his support for Communism as the only way for world society to progress towards peace and equality.

He had given extensive thought to the consequences of being found guilty of espionage. It was peacetime, so the maximum sentence would be fourteen years: he had made certain of that on several occasions. He was now thirty-eight. With time off for good behaviour he could be out of prison before he was fifty, hopefully with many years still ahead of him.

The Americans were deeply troubled when they learned of Blake’s treachery. Bill Harvey probably did not know whether to laugh or cry. He had always suspected that knowledge of ‘his’ Berlin tunnel had been leaked by the British, but to think that the Soviets had been aware of the plans prior to the breaking of ground for the tunnel’s construction was a far more serious matter. It was another staggering blow for the relationship between the CIA and MI6, just at a time when Allen Dulles and Sir Dick White had mended some of the fences previously knocked down by Burgess and Maclean, and by the still mistrusted Philby.

It did not help the Americans’ humour when, a week after Blake’s confession, the Soviet Union beat the United States in the race to put a man into space.

George Blake went on trial at the Old Bailey exactly a month after he had happily returned from his MECAS course in the Lebanon expecting a new posting and/or promotion. He was charged with five counts of offences under the Official Secrets Act, each relating to a specific period of time. He pleaded guilty on all counts. In his written statement Blake freely admitted that he had passed every official document of any significance he could access to his Soviet contacts.

The judge, the Lord Chief Justice of England, Lord Parker, sentenced Blake to the maximum of fourteen years on each of the five charges, the first three counts to run consecutively and the last two concurrently, making for a total prison sentence of forty-two years. At that time it was the longest sentence ever handed out by a British court. Blake, expecting no more than the maximum of fourteen years, was devastated.

On his return to London on 12 April, after his meetings with Penkovsky, Wynne contacted Dick Franks at MI6 Headquarters and arranged to meet him. He gave him Penkovsky’s letter and explained the circumstances that had led him to accept it. Wynne described the events of his visit to Moscow in detail, telling Franks he had a good feeling about Penkovsky and was sure of his sincerity.

Franks reported this to White and gave him Penkovsky’s letter. White called Wynne in for a thorough debriefing with Shergold, after which MI6 agreed to run Penkovsky in a joint operation with the CIA.

It was only a week until 20 April, the day on which the Soviet Trade Mission would arrive in London. The CIA and MI6 exchanged many telegrams, mostly between Shergold and Bulik, agreeing the ground rules for the joint management of Penkovsky and making arrangements for his debriefing in the UK.

In essence, MI6 would control Penkovsky in Moscow, at least until such time that the CIA could put someone in place to share the responsibility. Debriefing Penkovsky in London would be a joint operation run by two case officers on each team. MI6’s team was led by Harold Shergold, who was assisted by Michael Stokes, a Russian speaker. Shergold had greatly enhanced his already high reputation by extracting George Blake’s confession just two weeks earlier.

Joe Bulik led the CIA team, assisted by George Kisevalter. Kisevalter was born in St Petersburg, Russia. During WWI the Tsar sent his father to America to buy ammunition. He had his family – including young George, then seven years old – with him when the Russian Revolution started in 1917. The family remained in the United States, taking on US citizenship. George became one of the CIA’s most experienced case officers, having worked on such high-profile cases as Germany’s WWII intelligence chief Major-General Reinhard Gehlen and the GRU’s Major Pyotr Popov, before becoming involved in the Penkovsky case.

Kisevalter’s fluency in Russian and his outgoing personality made him the natural choice to take the leading role in debriefing Penkovsky.

* Kim Philby spoke openly in support of Communism when he was in Vienna and he married an Austrian woman who was an avowed Communist; yet he was never challenged about these conflicts with his MI6 work.

Yuri Gagarin became the first man in space on 12 April 1961.

Five years later, on 22 October 1966, Blake was helped to escape from prison. He made his way to Moscow where he still lives at the time of writing (August 2012).