By Hugo Gye
PUBLISHED: 03:16 EST, 13 November 2013 | UPDATED: 06:16 EST, 13 November 2013
Finding: Police have announced that MI6 spy Gareth Williams probably locked himself in the holdall where he was found dead in August 2010
The MI6 spy found dead in a holdall bag probably locked himself in and died by accident, police said today.
Gareth Williams' mysterious death has been the subject of fierce speculation since his body was found in his Central London flat three years ago.
A new review of the case by the Metropolitan Police has concluded that there is no evidence his death was the result of foul play, although they were unable to say for sure how he died.
The finding contravenes the verdict of a coroner who last year ruled that Mr Williams had 'probably' been killed by someone else.
Scotland Yard detectives said that since it was possible for the codebreaker to climb in to the bag and lock it unaided, it is not necessary to posit any outside involvement.
They added that there was no evidence of anyone else being in his flat at the time of his death, and no sign that the home had undergone a 'deep clean' to avoid incriminating a third party.
Deputy Assistant Commissioner Martin Hewitt said: 'With the conclusion of the investigation, the Metropolitan Police's position is that, on balance, it is a more probable conclusion that there was no other person present when Gareth died.
'But the reality is that for both hypotheses, there exist evidential contradictions and gaps in our understanding.'
Although he said that Mr Williams' death was 'most probably' an accident, he admitted: 'No evidence has been identified to establish the full circumstances of Gareth's death beyond all reasonable doubt.'
However, the family of the 31-year-old disagree with the verdict, according to police, and continue to support the coroner's theory that he was unlawfully killed.
They said in a statement: 'We are naturally disappointed that it is still not possible to state with certainty how Gareth died and the fact that the circumstances of his death are still unknown adds to our grief.
'We consider that on the basis of the facts known at present the coroner's verdict accurately reflects the circumstances of Gareth's death.'
Mystery: Last year a coroner ruled that someone else was involved in the codebreaker's death
Mr Hewitt admitted that the police and MI6 had failed to co-operate fully, but said it was 'beyond credibility' that his investigation had been deliberately deceived by anyone trying to hide the truth about Mr Williams' death.
'I do not believe that I have had the wool pulled over my eyes,' he said. 'I believe that what we are dealing with is a tragic unexplained death.'
Mr Williams, who was found dead inside the locked bag in the bath of his flat in Pimlico in August 2010, is known to have had an interest in escapology.
Coroner Fiona Wilcox last year ruled that the spy would not have been able to lock himself in the bag and was therefore likely to have died at somebody else's hands.
But within days of the verdict investigators claimed that it was in fact possible for a skilled escapologist to climb in to the red North Face holdall and lock it from the inside.
Last image: Mr Williams pictured on CCTV at a Tube station shortly before his death
Police launched a review of the case following the inquest, over concerns that some evidence had been handled improperly.
The investigation apparently included interviews with senior officials from MI6, where Mr Williams was working on secondment from GCHQ.
Confirmation that the spy's death was nothing more than a tragic accident could put to rest the various theories which have attached themselves to the case.
It has long been suspected that Mr Williams could have been targeted by foreign agents because of his highly sensitive MI6 work.
Another theory was that the Russian mafia assassinated him in a bid to stop him investigating money-laundering networks.
Others suspected that his death might have been the result of a sex game gone wrong, after it was claimed that he had close links with London's drag and bondage scenes.