George Blake, who died in Russia on Saturday at the age of 98, was the last in a line of British spies whose secret work for the Soviet Union humiliated the intelligence establishment when it was discovered at the height of the Cold War.

Britain says he exposed the identities of hundreds of western agents across eastern Europe in the 1950s, some of whom were executed as a result of his treason. His case was among the most notorious of the Cold War, alongside those of a separate ring of British double agents known as the Cambridge Five.

Unmasked as a Soviet spy in 1961, Blake was sentenced to 42 years in London’s Wormwood Scrubs prison. In a classic cloak-and-dagger story, he escaped in 1966 with the help of other inmates and two peace activists, and was smuggled out of Britain in a camper van. He made it through western Europe undiscovered and crossed the Iron Curtain into East Berlin.

He spent the rest of his life in the Soviet Union and then Russia, where he was feted as a hero.

Reflecting on his life in an interview with Reuters in Moscow in 1991, Blake said he had believed the world was on the eve of Communism.

“It was an ideal which, if it could have been achieved, would have been well worth it,” he said.

“I thought it could be, and I did what I could to help it, to build such a society. It has not proved possible. But I think it is a noble idea and I think humanity will return to it.”

In a condolence message published by the Kremlin, Russian President Vladimir Putin said Blake was a professional of particular vitality and courage who made an invaluable contribution to global strategic parity and peace.

“The memory of this legendary person will be preserved forever in our hearts,” he wrote.

Blake, who went by the Russian name Georgy Ivanovich, was awarded a medal by Putin in 2007.

“These are the happiest years of my life, and the most peaceful,” Blake said in the 2012 interview marking his 90th birthday. By then, he said, his eyesight was failing and he was “virtually blind”. He did not regret his past.

“Looking back on my life, everything seems logical and natural,” he said.

Though he worked separately from the Cambridge Five, Blake said that during his retirement he got to know two of them, Donald Maclean and Kim Philby.