A senior detective is to tell an inquest why her 21-month inquiry into the death of MI6 spy Gareth Williams has drawn a blank.

Detective Chief Inspector Jackie Sebire will be called along with Mr Williams's friend Elizabeth Guthrie on the second day of evidence.

Ms Guthrie appears after Scotland Yard was forced to apologise for "administrative errors" which led to them repeatedly spelling her name wrong.

Coroner Fiona Wilcox told a pre-inquest review "there has been some confusion" over Ms Guthrie's identity.

The inquest opened on Monday with Ms Wilcox hearing Mr Williams had been unhappy living in London and complained about "friction" at the intelligence agency. He hated the post-work drinking culture and "flash car competitions" at the Secret Intelligence Service (SIS), his sister Ceri Subbe said.

Mr Williams was due to move back to the West Country a week after his naked body was discovered padlocked inside a holdall in the bath of his flat in Pimlico, central London, on August 23 2010.

Detective Chief Superintendent Hamish Campbell, from the Met's homicide and serious crime command, said police were not shown any internal inquiry by SIS into what happened to the brilliant codebreaker. But he stressed that MI6 co-operated fully with Scotland Yard, adding that he was not aware of MI5, MI6 or SO15 carrying out independent investigations into Mr Williams's death.

Mrs Subbe told the inquest her brother was excited when he began what was supposed to be a three-year secondment to MI6 from GCHQ, the Government listening station based in Cheltenham. But he missed the countryside and became disillusioned with the atmosphere at MI6's Vauxhall Cross headquarters in London.

Mr Williams, of Anglesey, North Wales, failed to turn up for a meeting at MI6 on August 16, 2010, the inquest heard. The discovery of the spy's body curled up in a large holdall at his top floor flat in Alderney Street, Pimlico, sparked a painstaking investigation, worldwide media frenzy and several conspiracy theories.

Four intelligence agents will give evidence to the inquest anonymously in the coming days after Ms Wilcox said there was a real risk of harm to national security and international relations if they were exposed.