CAMBRIDGE spy Kim Philby declared he would have done it all again after finally confessing to being a Russian agent for years, according to newly declassified intelligence files.

The dramatic moment in January 1963 when he owned up after being confronted by his oldest friend, and fellow MI6 officer Nicholas Elliott, is vividly captured in a transcript of their conversation released to the National Archives in Kew, west London.

Philby admitted to his old friend in the Lebanese capital, Beirut, that he had been working for the Soviets since the 1930s.

According to the transcript, where MI6 secretly recorded their words, Philby immediately declared he was ready to open up.

He told Elliott: “I certainly would not have spoken to anyone else and when you yourself told me that you believed the evidence against me, that really did it.

“I have had this particular moment in mind for 28 years almost, that conclusive proof would come out.

“The choice actually is between suicide and prosecution. This is not in any sense blackmail, but a statement of the alternatives before me.”

He claimed that his change of heart had been due to the advent of Clement Attlee’s Labour government, which had brought in many of the things he believed in, and that confessing had been a “tremendous relief.”

Philby described his life in MI6 as a time of “controlled schizophrenia.”

“I really did feel a tremendous loyalty to MI6, I was treated very, very well in it and I made some really marvellous friends there,” he said.

“But the over-ruling inspiration was the other side.”

Philby added that “if he had his whole life to lead again, he would probably have behaved in the same way.”

A subsequent meeting between the pair saw Philby hand Elliot a six-page typewritten account of his recruitment and work for the Russians.

Before his confession, MI5’s top interrogator Jim Skardon, a former Metropolitan Police Special Branch detective, admitted he could not determine whether Philby was a Soviet spy, other declassified documents show.

At the conclusion of their interviews he admitted he found Philby to be “more of an enigma than ever.”

Another MI5 officer, Anthony Simkins, reluctantly admitted that Philby had given “no hint that he might be guilty” and they could do nothing without fresh leads.