A major review of security is under way at the bank

Colin Dundas, head of business banking, said on Monday that lessons had been learned following the robbery at its headquarters just before Christmas.

Police believe the raid on the bank's head office in Belfast on 20 December was carried out by the IRA.

However, the organisation has twice denied any involvement in what was the biggest cash raid in UK history.

"We continue to be a successful bank in terms of our security systems," said Mr Dundas.

"Certainly I would be sitting here comfortably thinking that something of this scale today could not re-occur."

Mr Dundas said the bank was learning quickly from what had happened.

"My belief is that we can never close out the risk that someone will try this but I am satisfied that in our initial learning zone, we have moved significantly forward in ensuring that something of this scale could not happen again," he added.

Chief Constable Hugh Orde has blamed the IRA for the raid

The IRA has twice denied it was behind last month's robbery in Belfast but NI Chief Constable Hugh Orde's assessment has not changed.

Police have a list of suspected IRA figures they believe were involved, names which have been included in security briefings given to government.

The IMC (Independent Monitoring Commission), which reports on paramilitary activity, met last week in Belfast to consider what it should do.

Its next report is not due until April but an earlier assessment is expected.