Code-breaker's body was found in padlocked bag

The cause of death is yet to be established after he was discovered in the government flat on 23 August, Westminster Coroner's Court heard.

But at the time of his murder, it is understood he was on secondment to Vauxhall Cross, the riverside headquarters of MI6, the Secret Intelligence Service, about half-a-mile from the flat in Alderney Street, Pimlico.

Officers discovered Mr Williams after breaking into the flat when the alarm was raised by colleagues who had not seen him for "some time". They found his body, as well as his mobile phone and several sim cards, laid out nearby at the top-floor flat.

Coroner Dr Paul Knapman revealed Mr Williams was found in a bag that was "padlocked shut" and the corpse appeared to be in an "advanced state of decay", a court spokeswoman said.

A post-mortem examination carried out on 25 August failed to establish a cause of death and investigations are continuing, the court heard. The inquest was adjourned to 8 September.

Dr Knapman will be kept informed of how the investigation is progressing and consider when to release the body so a funeral can take place, the court spokeswoman said.

Mr Williams, 30, was last seen alive eight days before his corpse was discovered. There were no members of his family in court.

Police have not said whether the sighting was made on CCTV or came from another source. The investigation is being led by the Metropolitan Police's Homicide Command with the security-vetted Counter Terror Command (SO15) also playing a lesser role in proceedings.

Officers are still trying to determine if Mr Williams was asphyxiated, poisoned or if drugs or alcohol were present in his system. A pathologist found Mr Williams was not stabbed or shot and there were no obvious signs of strangulation.

Mr Williams was days from completing a one-year secondment to the headquarters of the Secret Intelligence Service, MI6.