MI6 officer death: Gareth Williams mystery to endure
Despite a 21-month police investigation and an inquest, the coroner examining the death of MI6 officer Gareth Williams, whose body was found in a bag in his London flat in 2010, says it is never likely to be properly explained.
Mr Williams' entire working life was encompassed by secrecy. And his death has shed an unusually bright - sometimes harsh - light on parts of the secret service, as questions have been raised about any link to his work.
Mr Williams, who was 31 and from Anglesey, worked in a small office in MI6 headquarters, in Vauxhall Cross, London.
His role was to find ways of using the latest technology for covert intelligence collection - something he specialised in at GCHQ before being seconded to MI6.
In the past, MI6, which handles human agents or sources with intelligence, had worked largely separately from GCHQ, which deals with electronic communications. But in recent years the two organisations have moved closer.
Mr Williams was at the cutting edge of that increasingly important collaboration.
The technical wizardry Mr Williams worked on is one of the most secretive aspects of intelligence work and many details were out of bounds for the inquest on the basis of national security.
This sometimes led to intriguing but incomplete insights - a reference to Mr Williams using a different name was ended quickly.
But the senior witness from MI6 did try to clear up one issue - "[Mr Williams'] work… did not involve dressing in women's clothing," she explained in reference to the £20,000 of women's clothing found in his flat.
Mr Williams had originally joined GCHQ in 1999. He had a PhD aged 21 and was considered something of a "prodigy".
As his career progressed, he shifted from theoretical problem-solving towards the front line of intelligence collection.
No concerns over Mr Williams' private life were picked up in his original vetting by GCHQ or when it was reviewed by MI6. He was assessed as a very low risk.
GCHQ colleagues recalled a young man who was friendly, with a keen sense of humour and generally happy. GCHQ has tended to be a place where specialist skills and unusual people are valued.
But he was less content at MI6 - even though it was a secondment he had wanted, having reapplied after initially being turned down. His line manager (who gave evidence anonymously as Witness G) said he thought Mr Williams was an "introvert", although he acknowledged that Mr Williams was very good at the technical aspects of the job.
In early April 2010, Mr Williams asked to terminate his secondment early - an unusual move.
"He disliked the office culture, post-work drinks, flash car competitions and the rat race. He even spoke of friction in the office," his sister told the inquest.
"The job was not quite what he expected. He encountered more red tape than he was comfortable with."
Mr Williams' planned return to GCHQ in Cheltenham - due to happen two weeks after he died in August 2010 - had made him happier and more relaxed, colleagues said.
But was Mr Williams' work linked to his death? MI6 officials testified that there was no evidence to support that view. The lawyer for his family suggested otherwise.
Much of the evidence depended on interpretation and was open to competing views.
He did conduct a small number of searches of the MI6 database that did not appear to have any clear operational justification. The senior MI6 witness acknowledged this opened up a "theoretical possibility" that if a hostile party had learnt about this (or presumably some aspect of his private life) then this could have been used to put pressure on him.
However, officials said there was no evidence that either Mr Williams or any of his actions had come to the attention of any such agency or that they posed a threat to him.
Other aspects of the case fuelled suspicions. Why did his line manager fail to report Mr Williams missing for an entire week - even after he had missed a series of appointments and meetings?
The senior MI6 witness acknowledged that things went wrong and policies were not followed.
He said MI6 was "profoundly sorry" for the delay, which upset Mr Williams' family and affected the police investigation.
It meant Mr Williams' body had decomposed so much by the time it was found that it became significantly harder for pathologists to establish the cause of death.
The lack of significant DNA at the scene led lawyers acting for Mr Williams' family to suggest another person was present at the flat when he died and that this other person "was a member of some agency specialising in the dark arts of the secret services" or "evidence has been removed… by experts in dark arts".
That may provide one explanation but no clear motive emerged.
Mr Williams' office was another scene about which questions were raised.
The police officer in charge of the investigation only learnt about nine memory sticks found at MI6 during the inquest and the coroner questioned the impartiality of a vetted police officer who liaised with MI6.
Questions were also asked about whether electronic material had been properly secured at MI6 to prevent interference.
Those details, which could be explained by sloppiness, will do little to dispel the view held in some quarters that MI6 was not fully transparent and, in turn, the theory that it was somehow involved in the death or cleaned up.
The senior MI6 representative told the inquest that none of the service's officers had secretly visited Mr Williams' flat and that there had not been a cover-up.
But, even if it was his private life that led to Mr Williams' death, his life in the secret world will continue to add to the mystery that surrounds this case.