Police reveal MI6 code-breaker Gareth Williams was not alone at the time of his still unexplained death - a "striking piece of information", as Andy Davies explains.
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Mr Williams' body was found naked inside a padlocked holdall in his Pimlico flat on 23 August. The keys were inside the bag, and experts said the GCHQ codebreaker probably died a week before he was found.
Detective Chief Inspector (DCI) Jackie Sebire, who is heading the inquiry into his death, said today she was convinced someone else helped to put him there - after an expert brought in to examine the holdall concluded he could not have locked it himself.
"If he was alive he got into it voluntarily or, if not, he was unconscious and placed in the bag," she said.
Police also revealed the MI6 spy had visited bondage websites several times in the months before he died. The 31-year old accessed sites showing people tied up, including guides on how to do it yourself.
Detectives also said they had found tickets to a drag show, and that there was unworn women's clothing worth £15,000 in his wardrobe. They also said he had attended a fashion course.
But they said analysis of Mr Williams' phones and laptops revealed he visited no more than five bondage websites, and that there was no evidence he was "obsessed" with bondage and no other pornography was found. No bondage "paraphernalia or equipment" was found in the flat.
'Sex game gone wrong' theory
With the MI6's worker's interest in bondage, drag cabaret and women's clothing now revealed, the "sex game gone wrong" theory is emerging as perhaps the most plausible explanation for Gareth Williams' death. writes Channel 4 News Foreign Affairs Correspondent Jonathan Rugman.
Why not suicide? And why not murder? Suicide now seem less likely, as the police are "convinced" someone helped Mr Williams climb into the padlocked holdall in which he was found. But maybe this was misadventure involving others rather than outright murder.
The police say there is forensic evidence that other people were in the flat. The hunt continues for two possible suspects who have failed to come forward. Their failure to do so might suggest their involvement, though the police say they remain "completely open-minded" about how the Welshman died.
Were the missing persons accomplices in a sex game in which Williams inadvertently died? Or if they set out to kill him, what was their motive? None that we yet know of.
Crucially, British security sources still insist there are no known national security implications from Gareth Williams' death. In other words, if others were involved, there is no evidence we know of that they were terrorists. No evidence we know of that British secrets were stolen from Mr Williams, or that other lives have been put at risk.
Which is why, for now, the "sex game gone wrong" theory may came closest to an explanation for what is admittedly a still unexplained death.
There was also forensic evidence showing other people had been in Mr Williams' flat, although the police said they have not been able to track them down.
E-fit pictures have been released of a "Mediterranean couple" in their twenties who said they were visiting the flat in Alderney Street in late June or July. They were let into the communal block by another resident.
DCI Sebire said police were studying his private life in order to discover what happened to him. "We remain completely open-minded about how he died," she said.
"We are appealing today to someone who is out there to come forward and tell us more."
There was no evidence he was suicidal - and no evidence to suggest that he was gay - but she appealed for anyone who had had any contact with him to come forward, in case they could help to explain that side of his life. Police also said there were no signs of forced entry or a struggle at the top-floor flat and that none of his possessions were laid out in a "ritualistic" manner, as was reported after he died.
Mr Williams' death remained suspicious, and a conclusive cause of death still hasn't been found. An inquest will open at Westminster Coroner's court in February.