The driver of a van used to transport Jean McConville, the Belfast mother-of-10 shot dead by the IRA more than 40 years ago, may be living in Britain, police have revealed.
He was a teenager at the time, who left the city after the murder, but who later contacted the McConville family to disclose his part in her abduction.
Mrs McConville, 37, a widow, was taken from her home at Divis Flats in west Belfast in December 1972. Her remains were found on a beach in Co Louth in August 2003.
Detectives from the PSNI's serious crime branch, who are investigating the murder, are trying to trace the van driver who was aged around 16 at the time.
He was told to steal the van used in the abduction.
Mrs McConville was dragged from some of her screaming children and taken to a house in another part of west Belfast, believed to be Beechmount.
The driver left before she was taken away by the IRA and shot in the head for allegedly working as an informer for the British Army.
The allegation is vehemently denied by her family and Nuala O'Loan, the former Police Ombudsman, whose own inquiry into the murder was highly critical of the original investigation by the RUC.
The teenager moved to England shortly afterwards and only found out later Mrs McConville was murdered.
She was one of the 17 Disappeared, who were murdered by the Provisionals and secretly buried.
He contacted the family and spoke with one of her daughters, Helen McKendry.
It was the year before the first of two major excavation operations in 1999 just across the Irish border to try to locate the spot where she was buried.
Ms McKendry said: "He was very upset and he wanted me to know how he felt.
"He thought my mother was going to be returned to the family. He didn't identify himself, but it must have been playing on his conscience. He felt others should maybe clear their consciences as well."
A gang of 12, eight men and four women, are believed to have been involved.
One of them was allegedly Dolours Price, convicted of the 1973 Old Bailey bombing, who claimed she was ordered by Gerry Adams, now president of Sinn Féin, to abduct Mrs McConville.
Ms Price died last January, aged 61.
Mr Adams, a republican in Belfast at the time Mrs McConville vanished, has repeatedly denied any involvement in her murder, or that he was ever in the IRA.
Mrs McKendry, who met with him three times to discuss her mother's disappearance before the remains were found by a man out walking his dog at Shelling Hill beach, 80km from Belfast, said he should be interviewed as part of the new police investigation.
"I do not understand why he hasn't already been questioned. Why did they not arrest Dolours Price who took my mother to Co Louth? I hope Adams is questioned," she said.