Another person was most likely involved in the death of a British spy whose decomposing body was found padlocked in a holdall, an expert told the inquest into his death on Friday.
An inquest into his mysterious death has been looking into whether Williams could have locked himself into the North Face holdall as part of a sex game after examination of the spy's computer showed he had visited bondage websites.
But Peter Faulding, who specialises in rescuing people from confined spaces, told the inquest that even world-famous escapologist Harry Houdini would have found it a challenge to lock himself in the bag without help.
"My conclusion is that Mr Williams was either placed in the bag unconscious, or he was dead before he was in the bag," said Faulding, who made 300 failed attempts to lock himself into an identical holdall.
"I couldn't say it's impossible, but I think even Houdini would have struggled with this one," he added.
William MacKay, another expert in confined spaces, had earlier told the inquest he could not rule out the possibility that Williams acted alone.
"I would not like to say that it could not be done," MacKay told Westminster Coroner's Court in London, though he too had tried more than 100 times without success to lock himself in a bag measuring 81cm by 48cm (32 inches by 19 inches).
"There are people around who can do amazing things, and Mr Williams may well have been one of those persons," MacKay said.
Williams' family have said they believe secret agents versed in the "dark arts" tried to cover up his death, but police have unearthed no conclusive proof that anyone was with him when he died.
His home computer showed he had visited websites about claustrophilia -- the love of enclosure -- and bondage and sadomasochism, the inquest heard.
A video recovered from a mobile phone in the flat appeared to show Williams gyrating at the camera wearing only a pair of black leather boots.
High-end women's clothing and shoes worth some £20,000 ($32,400, 24,500 euros) were found in the immaculate flat.
The inquest, which was adjourned until Monday, has heard that forensic scientists cannot establish a cause of death because it took MI6 a week to realise he was missing.
Williams' boss at MI6 apologised on Thursday for failing to raise the alarm about his disappearance and conceded that the error may have hampered police inquiries because his body had decomposed by the time it was discovered.
Source: AFP European Edition