Russia 'has spy in UK's intelligence, cyber and security agency GCHQ', says ex-KGB defector
Defector and former KGB major Boris Karpichkov claims to have new evidence that the maths genius was murdered to protect Russia's mole
A Russian spy who infiltrated Britain's top secret Government Communications Headquarters (GCHQ) base is passing secrets to Moscow, a former major in the KGB says.
Defector Boris Karpichkov claims to have new evidence backing his dramatic claim that body-in-a-bag victim Gareth Williams was murdered because he knew the Russian mole's identity.
Maths genius and GCHQ codebreaker Williams, 31, was found dead, padlocked inside a holdall in the bath at his London home in August 2010.
At the time of his death he was on secondment to MI6.
Karpichkov, 56, who by coincidence lived near Williams' flat in Pimlico, south London, has been investigating the mysterious death ever since.
According to him, Moscow intelligence sources have confirmed that the Briton was murdered by the SVR, the KGB's successor, after a blackmail attempt failed.
The Russians had hoped to recruit Williams as a double agent in an operation codenamed Sweetie.
Moscow agents had discovered the spy's fondness for cross dressing and were threatening to reveal his secret unless he co-operated.
An inquest into his death heard how £20,000 worth of women's clothing was found at his flat.
Karpichkov believes Williams signed his own death warrant by defying the blackmail attempt.
He said: "Williams did not break down when confronted.
"But he recklessly said he knew the person who had tipped the Russians off about him.
"The SVR then had no alternative but to exterminate him in order to protect their agent inside GCHQ."
The SVR had kept Williams under intensive surveillance to gather "compromising material" on him after their GCHQ mole alerted them that his private life activities while at the communications and intelligence base in Cheltenham made him ripe for recruitment.
Russian spymasters had already put Karpichkov under a death sentence after he escaped to Britain 17 years ago - carrying two suitcases full of secrets.
The ex-KGB man noticed Russian diplomatic cars loitering in the Pimlico area of London in the days leading up to Williams' death and had made notes of their numbers.
Mistakenly, he became convinced that the Russian surveillance was aimed at him and that a hit squad was on its way to kill him.
Only after the death of Williams did he he realise the cars were actually there to monitor the MI6 operative.
Karpichkov recalled: "I had never seen those cars before - and I never saw them again."
The ex-KGB man claims that Williams was killed by pushing a needleless syringe containing untraceable poison into his ear.
He was then bundled into the bag because his murderers could not dispose of the body.
Karpichkov says an SVR clean-up team later returned to Williams' flat through a skylight and removed any remaining incriminating evidence.
Although the 2012 inquest said the death of Williams was "likely to have been criminally meditated" a subsequent police investigation came to the conclusion it was an accident.
They decided Williams had suffocated when a sex game went disastrously wrong.
Karpichkov believes different - and added: "As far as I know the mole is still operating inside GCHQ."