In a one-line statement the IRA, the most sophisticated of Northern Ireland’s rival paramilitary groups, said “We are dismissing any suggestion or allegation that we were involved.”

But given the scale of the crime, police haven’t ruled out paramilitary involvement, saying an IRA unit was one of five Northern Ireland gangs on its list of most likely suspects.

Other suspects include a unit of the major outlawed Protestant group, the Ulster Defence Association; the Irish National Liberation Army, a smaller rival of the IRA based in hard-line Catholic areas; and two other gangs with no political affiliations.

Although they’ve committed one of the world’s biggest robberies, experts believe the thieves will struggle to dispose of their booty.

Most of the money taken was Northern Ireland-produced notes, which are easy to track and hard to spend.

More than £13m of the bills stolen were newly minted notes produced by Northern Bank itself.

While Northern Ireland-issued currency is officially British pounds sterling, other parts of the United Kingdom usually refuse to accept it – and most of the rest of the world barely recognises it.

And as the size of the robbery has attracted huge attention, the entire global financial community is on alert for large volumes of used Northern Ireland notes.

Local police have denied they botched the operation over the robbery after it emerged they missed the robbers by a matter of minutes.

Officers went to the area after reports of suspicious activity near the bank’s headquarters on the night of the raid.

A foot patrol arrived five minutes later to check out the reported suspicious activity, apparently missing the gang by just a few minutes.

“When officers arrived here, there was no evidence of a crime. The gates were closed and it was some two hours later that a crime was reported to police – that wasn’t the police’s fault,´ said Detective Superintendent Andy Sproule.