Spotlight on private life of 'body in bath' spy

The spotlight was on the private life of GCHQ mathematics prodigy Gareth Williams as investigators hunted for clues to identify his killer.

The 30-year-old's decomposing body was found stuffed into a bag in the bath of his central London Government flat on Monday.

But the mystery over his final hours has since deepened after a post mortem examination failed to identify a cause of death.

Further tests will determine if the cycling fanatic was asphyxiated or poisoned, as well as if drugs or alcohol were present in his system.

A pathologist found Mr Williams had not been stabbed or shot and there were no obvious signs of strangulation.

Police have refused to categorise the case as a murder inquiry, despite the bizarre circumstances, as they insist he may have died innocently.

One line of inquiry is that he is the victim of sex game that went wrong and questions remain over why he was not discovered sooner.

Mr Williams was days from completing a one-year secondment to the headquarters of MI6 from his job at national "listening post" GCHQ in Cheltenham, Gloucestershire.

Police believe his body could have lain undiscovered for up to a fortnight and it is thought he was on holiday at the time of his death.

They suspect the key to the case could lie in his private life and are examining his mobile phone and financial records as well as closed circuit TV cameras around his home.

Investigators suspect Mr Williams might have known his killer as there was no sign of forced entry at his top-floor flat in smart Alderney Street, Pimlico.

His home has been the subject of a fingertip search amid fears that top-secret work material could have gone missing.

Mr Williams's parents Ian and Ellen travelled to London with his sister Ceri yesterday from their home in Anglesey to speak to police and formally identify his body.

A man who answered the door of their home said: "As you can imagine, it is hard enough at the moment and we have nothing to say."

Further details of Mr Williams continued to emerge as friends described him as a bright, quiet and determined man.

Childhood friend Dylan Parry, 34, said Mr Williams was academically gifted but socially naive and could be easily led.

Mr Parry, a volunteer at Westminster Cathedral, went to school with Mr Williams at Uwchradd Bodedern secondary in Anglesey, North Wales.

He told the London Evening Standard that Mr Williams travelled to Bangor University every week aged 16 to study for a mathematics degree part-time.

He said: "He was the kind of person who found it difficult to engage with people on a normal level. It was clear he was going to go far, but we all assumed he would end up in academia. Finding out he became a spy was a shock."

Mr Parry added that his friend was someone "people could easily take advantage of", that he was "naive" and a poor judge of character.

Fellow cyclists, including members of clubs in Cheltenham and Holyhead, paid tribute to Mr Williams for his skills after he clocked up a series of records.

One said: "He was a maths genius. People sometimes thought he was dense because he spoke rather slowly and sometimes seemed distracted."

Keith Thompson, of Holyhead Cycling Club, said he had known Mr Williams since he joined the club at the age of 17.

He said: "I never spoke to him about his job or his private life. Nobody did with Gareth. It was his cycling that we knew about."

Candidates face deep vetting

Potential employees of GCHQ face an intrusive vetting process that reaches into every corner of their private life.

Gareth Williams would have been subjected to "developed vetting" which includes interviews, background checks and a medical examination.

After graduating with a first class degree in mathematics, aged only 19, he went on to an elite course at St Catharine's College, Cambridge, but dropped out after apparently failing an exam.

The university is one of the traditional hunting grounds for intelligence community recruiters.

He would have faced extensive interviews including questions about his character and family history.

A risk assessment would have then been drawn up that goes beyond routine police and security checks.