Gareth Williams, 31, had been working for MI6 on a one-year posting but was due to return to his regular job at the GCHQ listening station in Cheltenham at the start of next month. Detectives believe Mr Williams, whose body lay undiscovered for up to two weeks in the bathroom of his top floor flat, might have had a violent row with a lover over his decision to return to Gloucestershire. However, police have not ruled out the possibility that the murder could be linked to his secret intelligence work. Nick Clegg, the Deputy Prime Minister, was given updates on the investigation as part of a scheduled intelligence briefing yesterday. Officers were yesterday examining Mr Williams’s mobile phone, which was found with several sim cards neatly laid out beside it, to find out his last contacts and when they were made. They were also studying CCTV images from cameras near the Georgian townhouse where Mr Williams had lived alone for the past year. There was no sign of forced entry at the flat in Pimlico, central London, suggesting the killer was someone Mr Williams knew. Nothing had been stolen. Scotland Yard said last night that a post mortem was inconclusive in establishing a cause of death and further examination, including toxicology tests, would be required. Sources played down reports that Mr Williams was stabbed. Detectives are studying whether he was strangled, asphyxiated or drugged.