An alleged al-Qaeda militant is being interviewed in Turkey over the murder of British engineer Ken Bigley in Iraq in October 2004.
Syrian Loa'i Mohammed Haj Bakr al-Saqa is being questioned by a Turkish prosecutor in the presence of British police.
Scotland Yard confirmed that British detectives had travelled to Istanbul to carry out inquiries into Mr Bigley's murder but refused to give any more details.
Turkish news agency Anatolia said al-Saqa was interviewed in the city of Kocaeli yesterday and reportedly told prosecutors an unnamed television station based in the United Arab Emirates had footage of Mr Bigley's death, which may hold answers to his murder.
In April last year a lawyer for al-Saqa said the body of Mr Bigley (62) was dumped in a ditch near the Iraqi city of Fallujah. However his body has still not been found.
Al-Saqa is currently on trial in relation to a series of terrorist bombings in Istanbul in 2003.
Mr Bigley's brother has welcomed the questioning of al-Saqa. Stan Bigley, from Wigan said he was "hopeful" it would lead to his brother's body being found.
Mr Bigley, an engineer from Liverpool, was taken hostage in Baghdad where he was working on September 16th, 2004.
The Government granted Mr Bigley an Irish passport in an effort to help secure his release. He qualified for Irish citizenship because his mother, Elizabeth, was born in Ireland. She originally lived in Ticknock, Co Dublin, before moving to Liverpool. The passport was granted following a request from the engineer's family.
Despite appeals on Al Jazeera television by Taoiseach Bertie Ahern, Sinn Féin president Gerry Adams and former SDLP leader Mr John Hume, Mr Bigley was beheaded three weeks after he was kidnapped.
Additional reporting: PA