In the second day of an interview with the head of the PSNI’s Serious Crime Branch, Detective Chief Superintendent Derek Williamson speaks to Crime Correspondent Deborah McAleese about the Omagh bomb, the Northern Bank robbery and the Robert McCartney murder trial

It is unlikely anyone will ever be brought to justice for three of the biggest crimes in Northern Ireland’s recent history, the head of the Serious Crime Branch said.

Derek Williamson said detectives are no longer actively working on the Omagh bombing, the Northern Bank robbery or the Robert McCartney murder.

However, Mr Williamson said if new investigative opportunities arise the cases will be reviewed.

He said he regrets that nobody has been made amenable for the crimes. The failed trials — which cost the public purse millions of pounds — led to serious criticism of the PSNI and the Public Prosecution Service.

“Have we made mistakes? Yes of course. We are human beings. 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.

“As the person now responsible for Omagh my assessment is that unless someone’s conscience pricks them and they come forward and tell us what they know or some key witness comes forward then unfortunately, investigatively we have done as much as we can. I have told the Omagh families this,” said Mr Williamson.

“It will always be regrettable that we haven’t made people amenable for all those murders. The same is true in those other investigations.

“Do we make mistakes? Yes. Do we regret them? Yes. Do we work hard to try and make sure we don’t make mistakes in the future? Yes.

“These cases remain open in the sense that if there is new evidence, if people come forward, we can go back and relook again. They are not open in the sense that we are actively working on them and investigating them.”

The Omagh bombing in 1998 was the largest single atrocity of the Troubles in Northern Ireland, claiming the lives of 29 people, one of who was a mother of unborn twins.

In 2007, after 56 days of evidence from 500 witnesses and a trial that cost millions of pounds, South Armagh man Sean Hoey was acquitted of involvement in the bombing.

Another blow for the PSNI and PPS came a few months later when the three men charged in connection with the murder of father-of-two Robert McCartney outside a Belfast pub were acquitted after a judge said the evidence was flawed.

And in October the case against the bank worker accused of stealing £26.5m from the Northern Bank collapsed when the prosecution announced that it would be offering no further evidence.