An unassuming and private character, Gareth Williams only ever described his work as "something to do with codes". Over the years he had grown accustomed to fading into the background. But when he repeatedly failed to turn up for work at the riverside headquarters of MI6, colleagues became so concerned that they called in Scotland Yard to open up his flat. From that point on Mr Williams' death – if not his life – was to be very public.
The scene that greeted the detectives inside the top-floor apartment of an expensive central London house was gruesome. A decomposing body had been stuffed inside a large sports holdall in the bath. Nearby, Mr Williams' mobile telephone had been laid out alongside several SIM cards.
Yesterday the 30-year-old's work as a communications officer at the intelligence "listening post" GCHQ, seconded to the Secret Intelligence Service, led to speculation that he had been brutally murdered because of his job. Was he the first spy to be killed in Britain since the former KGB officer Alexander Litvinenko was poisoned in 2006?
The reality, however, is likely to be more mundane. Sources within the murder inquiry led by the Metropolitan Police's Homicide and Serious Crime Command insisted that "the suggestion there are terrorism or national security links to this case is pretty low down the list of probabilities". They are believed to be concentrating on Mr Williams' private life.
While his body was discovered at around 4.40pm on Monday after the door to his flat was broken down, it appeared that he may have been dead for as long as two weeks. The first post-mortem examination proved inconclusive yesterday evening, though it did find that, contrary to earlier reports, he had not been stabbed.
Police have described the death as "suspicious and unexplained," and a further examination is due to be held soon to find out exactly how Mr Williams, yet to be officially identified, died. It will include toxicological analysis of his blood to test for traces of drugs or alcohol.
Both GCHQ and the Foreign Office have refused to say anything more than that it is policy not to confirm or deny the identity of any individuals working for the intelligence agencies. However, it is understood that Scotland Yard's Counter Terrorism Command and the domestic intelligence agency MI5 are being kept up to date with the investigation.
Mr Williams normally lived near his work within the heavily secure environment of the Government Communications Headquarters (GCHQ), an intelligence agency in Gloucestershire which eavesdrops on global communications. But he had been based in a flat in London for the past year in a street populated by bankers and politicians.
In a twist befitting any spy thriller, the property in Pimlico, whose recent occupants all appeared to have Cheltenham links, was owned by a company registered in the British Virgin Islands called New Rodina – a term which means "motherland" in Russian. The well-to-do street is home to a number of distinguished residents, including former Conservative Home Secretaries Michael Howard and Sir Leon Brittan.
It is a far cry from the granny flat in Cheltenham, with its floral carpets, silk flowers and potpourri, that he was about to return to on 3 September. His landlady Jenny Elliott, 71, said he had been a perfect tenant for 10 years and she had welcomed his return when he called a fortnight ago to ask whether he could move back.
He was, she said, a fairly reclusive person, whose parents and sister had only visited once: "Gareth was a really nice and quiet man, but he didn't really seem to have much of a circle of friends. As far as I'm aware, he never bought a girl back in the 10 years I knew him... Gareth occasionally said he was 'meeting some of the guys from work for a quiet drink', but he wouldn't tell me who they were or where they were going and I never pried. "
Often she would hear him working late into the night: "All I heard was a tape recorder being rewound or listened to over and over, although he must have had his earphones in because I couldn't make out what it was."
"It's a real tragedy what's happened. Gareth was a really nice guy who was polite and mild-mannered and wouldn't hurt a fly," explained Mrs Elliott, adding: "He was a cycling fanatic and was forever off on some bike ride or another. He was an extremely intelligent person but would not talk about his job as it was a secret, on account of working for GCHQ. All he told me was it was something to do with codes."
Last night his uncle, William Hughes, from his home town of Anglesey, explained that he had not even told his family what work he was doing in London, only that he was employed by GCHQ. The news of his death was broken to his parents on holiday.
"It was a terrible shock," he said. "I got a phone call yesterday morning. I couldn't believe that such a thing had happened. At the time we didn't have any details – just that he'd been found in his flat. He was quiet, unassuming. When he came home on his weekends and holidays he'd be on his bicycle, riding around the lanes of Anglesey."
Brilliant academically, he had attended a special primary school, Mr Hughes explained. "He was a very clever lad. When he was at secondary school he would go to university one day a week." In 2000, he attended St Catharine's College, Cambridge, to undertake a notoriously demanding postgraduate certificate in advanced mathematics only open to students with first-class degrees in physics, maths or engineering, but dropped out a year later.
Yesterday, as forensics officers continued to examine the flat behind a police cordon, neighbours said Mr Williams had been a pleasant man, who kept his curtains closed so it was hard to tell whether he was in. One neighbour, Eileen Booth, 73, said detectives had called looking for information and said the murder may have taken place two weeks ago.
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 heard the news in a text message yesterday morning and it was a shock.
"We are a small club, only 20 members, and all of us knew Gareth.
"We are totally devastated. He was a really lovely young man.
"Of course, once he moved to Cheltenham he joined the club there and we didn't see much of him.
"I last saw him on our Boxing Day meeting last year.
"He was his usual self really.
"It's true that he was very quiet. He wasn't a great conversationalist.
"We were club mates but Gareth wasn't the sort to go the pub after a race so he didn't have any close friends in the group.
"I never spoke to him about his job or his private life. Nobody did with Gareth.
"It was his cycling that we knew about. He was known for being very good on hill races but a couple of times he won the club's 'best all-rounder' award.
"He was also a good runner but that was to be expected, his whole family is very sporty.
"His father was a member of this club and Ceri was an athlete.
"We'll be getting in touch to offer our condolences when they are home.
"We have also cancelled a club event we had planned for tonight. Nobody feels up to it now."
David Hughes, from Clwb Rasio Mona, another cycling club on the island, said: "As neighbouring clubs, we used to come across each other all the time.
"Although I didn't know him personally, he was known around the cycling scene as a lovely person.
"His reputation was for hill races and he was a fine sportsman."