Northern Ireland's chief constable has said he is not hopeful anyone will be brought to account over the IRA murder of a Belfast mother-of-10.
Jean McConville was abducted and murdered in 1972
Sir Hugh Orde was speaking after a report by the Police Ombudsman criticised the investigation into the murder of Jean McConville in 1972.
It said a proper investigation was not carried out for more than 20 years.
Sir Hugh said: "Any case of that age, it is highly unlikely that a successful prosecution could be mounted."
Mrs McConville, who was a widow, was abducted and killed after she went to the aid of a fatally wounded British soldier outside her home in west Belfast's Divis flats.
The Police Ombudsman found there was no formal police record of Mrs McConville's disappearance, nor of attempts at the time to find her.
The chief constable told a news conference: "We are very sorry for what happened. It should clearly have been investigated better."
He said he and his officers would be willing to meet the family to update them on the progress of their investigation.
Sir Hugh, who has set up the Historical Enquiries Team to deal with unsolved murders during 30 years of violence in Northern Ireland, insisted it would do everything possible to bring some form of resolution for the McConville family.
In a statement earlier, the police said they "apologised unreservedly to the family for any failings made by police".
"Police policy and practice into how it deals with missing persons and how it conducts investigations has changed significantly since 1972," it said.
Deputy Chief Constable Paul Leighton said that in 1972 more than 470 people were murdered in Northern Ireland and people had to realise what the situation was like then.
"There were over 10,000 shooting incidents, these are statistics that are difficult nowadays to comprehend," he said.
"I am not using that as any excuse for failure in police action.
"I think if there is a failure in police action, then we need to say sorry and that is what I am doing, but I think it is important for people to realise just what the situation was at that time."
Mrs O'Loan's investigation upheld a complaint brought by two of Mrs McConville's children.
Her report found there had been intelligence that she was still alive some time after being abducted from her home in December 1972.
The IRA insists the mother-of-10 was a British army informer, although a police ombudsman inquiry earlier this year found no evidence of this.
Mrs McConville's remains were finally found at Shelling Hill beach in County Louth in the Irish Republic in August 2003.
Mrs O'Loan said: "By 16 January (1973) a spokesman was being quoted as saying the matter was being investigated but we have found no evidence of this.
"There is no crime file about any investigation of the abduction in 1972.
SDLP MLA Alex Attwood said it was a 'deep indictment' of the RUC
"Even if we look at the intelligence the police received which suggested that Mrs McConville was alive and had either left of her own will or was being held by the Provisionals in Dundalk, we found no evidence that either of these issues were looked at.
"An Garda Siochana (Irish police) have said they are not aware of an investigation by them into Mrs McConville's death prior to the discovery of her body."
Mrs McConville's son Michael said he felt vindicated by the report.
"They didn't do enough work on the case in the first place, I think it was a big let down for the McConville family," he said.
"If police had reacted more quickly, my mother might have still been alive today. I think that to start an investigation 20 years later is a bit late."
SDLP assembly member Alex Attwood said the report was "a deep indictment of the Royal Ulster Constabulary".
"Questions must be answered by the police about their approach, and questions must continue to be put to the IRA to ensure that they account fully and publicly for their actions."