A notorious British double agent who worked for the royal household and taught at Cambridge University, has said spying for the Soviet Union was the "biggest mistake" of his life.
In a posthumous memoir opened for research by the British Library on Thursday, Anthony Blunt -- an upper class, Establishment figure -- also said he chose to stay back in Britain rather than flee to the former Soviet Union when he was publicly denounced as a traitor and even contemplated ending his life.
Blunt, a Trinity College don and noted art historian, doubled up as a 'talent spotter' and member of the notorious World War II and 1950s 'Cambridge Spy Ring,' whose other members were Harold 'Kim' Philby, Donald McLean, Guy Burgess and John Cairncross.
Blunt, who was also the Surveyor responsible for maintaining the royal collection of paintings, admitted to being a Soviet spy in 1964 and was publicly unmasked by former prime minister Margaret Thatcher in 1979.
After his public exposure, he wrote a 30,000-word memoir, which was donated anonymously to the British Library in 1984 -- the year after his death -- on condition that it remained secret for 25 years.
In the memoir, Blunt, a wartime agent for the British spying agency MI5, said despite his enthusiasm for Soviet communism, he was persuaded not to join the British Communist Party by fellow spy Guy Burgess.
"I might have joined? but Guy, who was an extraordinarily persuasive person, convinced me that I could do more good by joining him in his work," he wrote.
"What I did not realise at the time is that I was so naive politically that I was not justified in committing myself to any political action of this kind.
"The atmosphere in Cambridge was so intense, the enthusiasm for any anti-fascist activity was so great, that I made the biggest mistake of my life."
As war clouds gathered over Europe in the late 1930s, Blunt said he decided "the ivory tower no longer provided adequate refuge".
Both Blunt and Burgess were homosexual, but Blunt said they were not sexual partners.
Blunt said although he did not much care for undergraduate Burgess initially, he was later won over by "the liveliness and penetrating quality of his mind" and interests.
"He could be perverse both in argument and behaviour, but in the former he would wriggle back to sense and in the latter he would apologise in such an engaging manner that it was difficult to be angry for long.
"His sex life was already fairly full, but he did not blazon it about as he was to do later."
When they shared a house in central London during the war years, Blunt said: "It is true that Guy had a number of friends who visited him regularly, but it was a rule of the house that casual pick-up was forbidden and Guy observed this rule."
After Maclean and Burgess fled to Russia in 1951, Blunt came under suspicion but refused to follow their example because, he wrote: "I realised quite clearly that I would take any risk in this country, rather than go to Russia."
He was eventually denounced in 1964 and confessed when offered immunity, giving the authorities "all the information that I had about the Russian activities".
He was allowed to return to work -- in exchange for cooperation with the MI5 -- and he continued with the royal post until 1972, saying "I believed, naively, that the security service would see it, partly in its own interest, that the story would never become public."
His sudden public exposure by Thatcher, who named him in parliament in 1979, came as an "appalling shock", he wrote, but he decided not to kill himself: "Many people will say that it would have been the 'honourable' way out? I came to the conclusion that it would on the contrary be a cowardly solution."
"It would have made things as bad as possible for my family and friends; they would have had the double shock of my suicide and the revelations which would have followed immediately."
Instead, he sought refuge in "whisky and concentrated work" on his memoir and a number of books on art history.
According to the media reports of the time, Blunt went into hiding in Europe after the public shaming.
Returning to London years later, he tried to slip into a cinema in the London neighbourhood of Notting Hill one day, but was recognised and booed until he was forced to leave the auditorium.