Three of the biggest crimes in Northern Ireland’s recent history are no longer being actively investigated, the head of the Serious Crime Branch has said.

Detective Chief Superintendent Derek Williamson told the Belfast Telegraph it is unlikely anyone will ever be brought to justice for the Omagh bombing, the Northern Bank robbery or the Robert McCartney murder.

But he stressed that the cases will be looked at once again should new investigative opportunities arise.

“It will always be regrettable that we haven’t made people amenable ... Have we made mistakes? Yes of course ... We try to do the best we can. Is it a prospect that we could go back over those cases?

“If new evidence comes to light then yes, we would investigate them. Never say never,” Mr Williamson said.

A total of 29 people, including a mother pregnant with unborn twins, were killed during the Real IRA bombing of Omagh.

The only person ever to stand trial for the atrocity was acquitted following a multi-million pound trial.

The bank worker accused of the Northern Bank robbery, the biggest cash robbery in British history at the time — and the three men charged in connection with the murder of Belfast man Robert McCartney — were all also acquitted.

The Northern Bank raid, followed swiftly by Mr McCartney’s murder, threatened to unravel the restoration of Stormont because of the reported IRA involvement in both crimes.