[4] Two senior British police sources have said some of Williams's work concerned Russia – and one confirmed reports that he had been helping the US National Security Agency trace international money-laundering routes that are used by organised crime groups including Moscow-based mafia cells.

[5] Originally from Valley, Anglesey, Wales,[6][7] Williams, who spoke Welsh as a first language, began studying mathematics part-time at Bangor University, while still attending his secondary school, Ysgol Uwchradd Bodedern, and graduated with a first-class degree at age 17.

[8] After gaining a PhD at the University of Manchester, after failing an exam,[9] he dropped out from a subsequent post-graduate course at St Catharine's College, Cambridge,[6] and took up employment with GCHQ in Cheltenham in 2001,[10] renting a room for nearly a decade in Prestbury, Gloucestershire.

Reportedly an intensely private man and a keen cyclist, Williams was due to return to Cheltenham on 3 September 2010, after spending a year in London, following his annual leave.

[11][12] The local police had gained entry into the top floor flat at 36 Alderney Street,[13] Pimlico at around 16:48; on examination of the bag, the premises were declared a crime scene.

[2] A forensic examination of Williams's flat has concluded that there was no sign of forced entry or of DNA that pointed to a third party present at the time of his death.

[1] Scotland Yard's inquiry also found no evidence of Williams's fingerprints on the padlock of the bag or the rim of the bath, which the coroner said supported her assertion of "third-party involvement" in the death.

Metropolitan Police Deputy Assistant Commissioner Martin Hewitt said it was theoretically possible for Williams to lower himself into the bag without touching the rim of the bath.

[28] Anthony O'Toole, the lawyer for the family, said at the coroner's inquest in March 2012 that a second person was either present when Williams died, or someone broke in afterwards and stole items.

DNA found on Williams's hand turned out to be contamination from one of the forensic scientists and the police determined that a Mediterranean couple they had been seeking had nothing to do with the inquiry.

[30] LGC, the forensic company, apologized that the error had inflicted such pain on the family, caused by the incorrect data entry of a numerical code.

[33] Journalist Duncan Campbell reported that the inquest evidence indicated Williams was one of a team of intelligence officers sent to penetrate US and UK hacking networks.

The coroner was critical of SIS for failing to report Williams missing for seven days, which caused extra anguish and suffering for his family, and led to the loss of forensic evidence.

Metropolitan Police Deputy Assistant Commissioner Martin Hewitt announced that despite a re-examination of all evidence and the investigation of new leads, no definitive answers had been obtained as to the cause of Williams's death, and the "most probable scenario" was that he had died alone in his flat in Pimlico, central London, as the result of accidentally locking himself inside the bag.

The miniseries stars Ben Whishaw as Danny, who is accused of murder after his partner, MI6 spy Alex, is found dead inside a locked trunk.