Secret meeting between MI6 and police hours after discovery of spy Gareth Williams's death Mr Williams, who worked at the Government's listening centre GCHQ, was on secondment to MI6 when his body was found. The alarm was raised after he failed to turn up to work for over a week. His family, in Holyhead, north Wales, believe his death may have been linked to his work at MI6, where he had recently qualified for "operational deployment." They fear that fingerprints, DNA and other evidence was wiped from the scene in a deliberate cover up. Anthony O'Toole, the barrister representing the family, told an interim hearing ahead of the inquest last month that Mr Williams could have been killed by someone who specialised in "the dark arts of the secret services." He later added: "To properly explore the circumstances of his death we do need to know something of the deceased's work." Among the matters discussed by Sir John and Sir Paul during their meeting, which is thought to have been held at Sir John's private dining room at SIS headquarters, in Vauxhall, was the question of which senior officer was to head the investigation. It is understood that Sir John expressed his satisfaction with the choice of Detective Chief Inspector Jackie Sebire as lead officer in the inquiry. An intelligence source said: "SIS wanted to make sure that the Met didn't stray too far into the question of what Gareth Williams's job entailed. They did not want any potential leaks over the nature of his work for the NSA, GCHQ or MI6. It has also emerged that the US State Department asked MI6 to ensure that no details of Mr Williams's work should emerge at the forthcoming inquest. US officials asked SIS to raise the matter with the Foreign Office. Sir John, who attended Mr Williams's funeral, is understood to have discussed the matter with William Hague, the Foreign Secretary. Mr Hague subsequently signed a public interest immunity certificate authorising the withholding of details from the inquest about Mr Williams's secret work and joint operations with the Americans. it is understood that as a result NSA and FBI officers who would have been called as witnesses at the inquest will no longer be asked to attend. Mr Williams had been working at NSA shortly before his death, where he was helping to develop a joint GCHQ-NSA defence against cyber attack's on the west's computer infrastructure, particularly in the banking and transport sector. At one stage during his work at NSA, shortly before he returned to London, Mr Williams was given security clearance to visit its facility in the Utah desert, which the agency classifies as "above top secret." Mr Williams also spent several months at Menwith Hill, the secret listening station in Yorkshire used by the United States to intercept coded messages, and Fort Meade in Maryland, the home of the NSA. Police told the interim hearing that experts were agreed it was impossible for Mr Williams to have locked himself in the holdall before his death. Mr O'Toole said that if he had not locked the bag himself, there was "a high probability that there was a third party present in the flat" at the time. He suggested that "the unknown third party was a member of some agency specialising in the dark arts of the secret services, and perhaps evidence was removed from the scene post mortem by an expert in those dark arts." Outside the hearing, Mr O'Toole said the family did not know whether the "third party" might have belonged to a British or foreign agency. An intelligence source said: "Given the sensitivity of the situation, both Hague and Hillary Clinton, US Secretary of State, would have been kept informed after the claims made by the Williams family barrister." There has been speculation that either the Russian or Chinese security services could have been responsible for Mr Williams's death. SVR, the Russian foreign intelligence service, is understood to have around forty spies in this country. They are either working under diplomatic cover at their embassy or with trade missions. MSS, the Chinese foreign intelligence service, is believed to have staff of over three thousand based in every country, including a number of 'hit" teams. Britain's three main intelligence services - MI6, MI5 and GCHQ - have a number of safe-houses in and around London. They are used as bases to interrogate foreign spies before they are handed over to Scotland Yard for arrest and trial and to brief or debrief an officer before or after a mission. They also provide accommodation for an officer in transit from one posting to another, as in Mr Williams's case. His Pimlico safe-house had an unlisted number which gave him direct contact with MI6. All his calls were logged on the service's switchboard facility. These were later checked and apparently produced no clue to assist the police. Scotland Yard said it was not prepared to discuss details of the investigation into the death of Mr Williams, which its says remains an ongoing inquiry.