Revealing new insight into Britain's most infamous spy has finally come to light following the publication of a secret video showing his long-term career as a double agent for the Soviet Union.
In previously unseen footage recovered by the BBC, Kim Philby, the ex-MI6 officer who rose up the ranks of British intelligence before defecting to become a Russian spy, said he regularly passed on top secret information to his Soviet contacts "year in, year out".
The new footage is taken from a secret lecture given by Philby in 1981, where he is seen briefing the East German Intelligence Service, the Stasi, about his life as a double agent.
It is the first time that footage of the former MI6 officer has been released to the public, and reveals Philby talking about his career rising up through the ranks of MI6 while secretly passing on intelligence to Soviet contacts in the KGB.
During the video, Philby, who was known during the Cold War as Britain's biggest traitor, warns the audience that he is "no public speaker", adding that he "spent most of my life trying to avoid publicity of any kind".
"You have probably all heard stories that the SIS (Secret Intelligence Service) is an organisation of mythical efficiency, a very, very dangerous thing indeed," he said.
"Well, in a time of war, it honestly was not.
"Every evening I left the office with a big briefcase full of reports which I had written myself, full of files taken out of the actual documents, out of the actual archives.
"I used to hand them to my Soviet contact in the evening. The next morning I would get the file back, the contents having been photographed, and take them back early in the morning and put the files back in their place.
"That I did regularly, year in, year out."
Until the BBC made the discovery at the official archives of the Stasi in Berlin, only one video of Philby speaking was known to exist.
Born in the Punjab, India, on January 1 1912, Philby was first recruited by Britain as an Officer of the Order of the British Empire in 1946. He was only exposed as a Russian double agent in 1963, by which time he is believed to have spent years passing on top secret documents to the KGB.
Educated at Cambridge University, Philby reveals in the video that he was first drawn to communism during his days as an undergraduate.
He would later be exposed as a member of the spy ring known as the Cambridge Five - a group educated at Cambridge and recruited by the Soviet Union during the Second World War.
Philby also discloses that despite being born into the "British governing class", it was his belief that he had spent "30 years in the enemy camp".
Before his public exposure, Philby rose to become a high-ranking figure in MI6's Anti-Soviet division, where he was encouraged by his KGB employers to unseat his boss in order to become "head of that new department".
In an admission never aired before, the Soviet turncoat revealed that he "set about the business of removing my own chief", drawing laughter from the audience.
"It's a very, very dirty story, but after all our work does imply getting dirty hands from time to time," he added.
The video ends with Philby answering a number of questions from East German spies, during which he advises them to never confess during interrogation.
Created and archived in secrecy, the footage is the first and only evidence of Philby coming close to a full confession.