The mystery death of MI6 spy Gareth Williams was not the result of assassination by security services, police investigating the incident believe.
In one of the most bizarre deaths of recent times, Williams was found naked and locked inside a sports bag inside his home in central London in 2010. The decomposing corpse was found when his flat was searched because he had failed to turn up for work.
According to the Telegraph, police believe it is most likely that Williams died alone. The cause reportedly favoured by Scotland Yard is that Williams died during "auto-erotic activity" relating to confinement.
That flies in the face of coroner Dr Fiona Wilcox's ruling at the inquest earlier this year into his death. She dismissed a sexual motive in her findings. His death was found to be "unnatural and likely to have been criminally mediated", she ruled.
Although detectives do not think there was foul play, they have struggled to work out how the body of the MI6 codebreaker ended locked up inside the small bag along with the keys.
Two experts made 400 attempts to mimic Williams' alleged actions - clambered into the sports bag unaided and locked himself into it from the inside. They found that it was improbable.
But police investigators have continued to be stumped by the absence of evidence of a second party at the scene, such as footprints.
Days after the inquest verdict a retired army sergeant showed how it was possible to climb into a similar North Face bag and lock it from the inside.
Scotland Yard detectives have now been able to repeat the experiment with some slight differences to the way Williams' bag was locked.
Lines of enquiry pursued by police continually turned up nothing, including a hunt for a shadowy Mediterranean couple subsequently ruled out.
A trawl by police of Williams' web usage revealed he had visited sex websites specialising in bondage and claustrophilia - the thrill of being enclosed in confined spaces.
He kept pictures of drag queens on his computer and had £20,000-worth of designer women's clothes in his flat along with women's shoes and wigs.
Friends and family of Williams have always refuted claims he died after a sex game went wrong, speculating that it was linked to agency "specialising in the dark arts."
A Scotland Yard spokesman said: "This remains an active investigation and officers continue to explore a number of lines of enquiry. Officers retain an open mind in relation to the circumstances surrounding the death of Mr Williams."