Death of Gareth Williams

Gareth Wyn Williams (26 September 1978 – c. 16 August 2010) was a Welsh mathematician and Junior Analyst for GCHQ on secondment to the Secret Intelligence Service (SIS or MI6) who was found dead in suspicious circumstances in Pimlico, London, on 23 August 2010, at a flat used to house Security Service's staff. The inquest found that his death was "unnatural and likely to have been criminally mediated." A subsequent Metropolitan Police re-investigation concluded that Williams's death was "probably an accident".

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.