British police say a MI6 agent found dead locked inside a sports bag probably locked himself into the sports bag where his naked body was found and was not the victim of a hit by the security services.
Cryptology expert Gareth Williams, 31, worked for Britain's secret eavesdropping service GCHQ but was attached to the MI6 overseas spy agency when his remains were found in August 2010 inside the bag in a bathtub at his London apartment.
A British coroner ruled in May that another person was likely to have been involved in Williams' death, adding that she could not rule out the involvement of the spy agency.
But a Scotland Yard review of the case sparked by that ruling has concluded that he probably died alone, the Daily Telegraph reported.
The murder squad has spent seven months re-interviewing Williams' colleagues from MI6 and has taken DNA samples.
"They have been unable to find any trace of anyone who should not have been in the flat and every reason to believe that Gareth may have climbed into the bag himself and been unable to get out," a source close to the inquiry said.
Coroner Fiona Wilcox said it was unlikely that the death would ever be "satisfactorily explained," but she said the spy was likely killed either by suffocation or poisoning in a "criminally meditated act."
She said he could not have climbed into the bag and locked it himself. Two different specialists attempted to recreate the feat without success.
Williams was discovered in the foetal position inside the bag with two keys to the bag's padlock underneath his buttocks.
Williams, described as an introverted math genius, worked for Britain's secret eavesdropping service GCHQ.
But he was attached to the MI6 foreign spy agency when his remains were found, just a few days after returning from a trip to the United States.
Forensic experts found some £20,000 (NZ$39,965) worth of luxury women's clothing, shoes and wigs in his apartment.
Police also discovered that he had visited bondage and sadomasochism websites, including some related to claustrophilia - a desire for confinement in enclosed spaces.
William's landlord testified during the coroner's hearing that she once found him handcuffed to his bed. She said he had appeared embarrassed after asking for help.
When the case emerged, some had speculated that he could have been the target of Russian criminal gangs or an al Qaeda extremist.
Other media reports had said there had been a break-in at the property where he lived - a building sometimes used by MI6 to house its agents.
MI6 waited a week to investigate why Williams hadn't shown up for work - a delay that made it difficult for Williams' family to identify his badly decomposed body.
During the coroner's hearing, MI6 accepted that Williams disliked the agency's boozy culture of post-work drinking and tedious bureaucracy, and had requested to return to his job at GCHQ.
One MI6 officer claimed that Williams hadn't been reported as missing because colleagues assumed he was preparing for his return to the southern England headquarters of the eavesdropping service.