Race to solve secret of grisly murder in an MI6 'safehouse'
The discovery of the body of the former University of Cambridge student, named as Gareth Williams, led to feverish speculation about the nature of his death, with detectives trying to establish whether or not it was connected to his work with the intelligence agencies.
Mr Williams, in his 30s, was employed as a communications officer at the GCHQ "listening post" in Cheltenham, Gloucestershire.
But at the time of his murder, it is understood he was on secondment to Vauxhall Cross, the riverside headquarters of MI6, the Secret Intelligence Service, about half a mile from the flat in Alderney Street, Pimlico.
Officers discovered Mr Williams after breaking into the flat on Monday afternoon when the alarm was raised by colleagues who had not seen him for "some time".
They found his body, as well as his mobile phone and several sim cards, laid out nearby at the top-floor flat.
A Home Office pathologist yesterday began a post mortem examination to learn exactly how Mr Williams, died.
The officer was described by one Pimlico neighbour as "extremely friendly".
Sources close to the inquiry played down speculation that the murder was linked to his secretive line of work.
One source said: "The suggestion there is terrorism or national security links to this case is pretty low down the list of probabilities."
Whatever the cause of his death, Mr Williams' murder is a severe blow to MI6 and follows last month's court case that saw former MI6 worker Daniel Houghton admit charges of unlawfully disclosing top-secret material.
The Houghton case resulted in questions being raised about the suitability of the people being recruited by MI6.
Last night, the murder led to intelligence experts suggesting that if it was found Mr Williams had put himself in a dangerous situation, then more questions about MI6 vetting procedures would be posed. Writing in The Scotsman, Professor Anthony Glees, an academic specialising in intelligence matters, suggested that "these processes are not working as well as they should".
Professor Glees added: "It is always possible that Mr Williams was simply in the wrong place at the wrong time."
But Prof Glees, the director of the Centre for Security and Intelligence Studies at the University of Buckingham (BUCSIS), added: "It is peculiar if this flat was, as I suspect, a Secret Intelligence Service safehouse, that someone got into the house to commit the crime without being invited in. That would be very worrying."
According to Prof Glees, if a dangerous individual had entered the Pimlico flat because Mr Williams was speaking to him in a professional capacity, then there would have been someone else from the secret services present.
"Cases like this tend to have something to do with a person's private life - whether that it is something to do with unusual sexual activity or drug dealing," Professor Glees said.
The Pimlico flat's proximity to MI6's HQ and the fact that it is owned by a company called New Rodina, registered in the British Virgin Islands, led Professor Glees to surmise it was a secret services safehouse. The word rodina means "motherland" in Russian and Bulgarian.
The property was bought for 675,250 in 2000 and remortgaged twice.
Before Mr Williams' secondment to London, he had lived in a flat in Cheltenham for the last ten years. He was preparing to return there next month.
In London, neighbours described Mr Williams as an "extremely friendly" and athletic man who enjoyed cycling and had a strong Welsh accent.
Laura Houghton, 30, a secretary, said: "His windows were always shut and curtains were often closed. I could never tell if anyone was in.
"It was strange that we never saw him come and go. I just assumed he worked away."
Eileen Booth, 73, who lives opposite, said detectives told her the murder might have taken place two weeks ago.
"A few years ago, I would definitely have known who it was that had been killed. But nobody knows each other these days," she said.
The scene of the murder is a two-storey flat on a prestigious street among a row of expensive five-storey Victorian townhouses.
Residents of the prestigious street include former home secretaries Michael Howard and Lord Brittan. Public documents revealed several current and former residents of the freehold block have links to London and Cheltenham.
Last night, Mr Williams' parents were on their way to London. His uncle William Hughes said he had no idea of the type of work the spy did.
"He worked for GCHQ for many years. I knew he was working in London doing something," Mr Hughes said.
"He would never talk about his work and it felt rude to ask, really."