A pensioner was on security duty at the time the Northern Bank was robbed of £26.5 million, it emerged tonight.
He had been monitoring CCTV screens as the vaults were cleared by two members of staff whose families were being held hostages.
The guard is understood to have been employed by Maybin, an outside security agency hired to protect the Northern's cash distribution centre.
New details emerged as bank chiefs admitted their security arrangements were not as effective as they should have been, and confirmed a major review was under way following the raid which police chiefs have blamed on the IRA.
It is believed to involve a study of the CCTV and swipe card systems, as well as the possibility of relocating the distribution centre from its current Belfast city centre base.
Mr Colin Dundas, head of business banking at the Northern said: "Our whole security process will be looked at, as part of a review. We have already taken some learnings out of that and made some changes. "There's no question that given the scale of the robbery it wasn't effective on the day."
Mr Dundas confirmed Maybin staff were used to guard the bank after a study was carried out to check they had the expertise needed. No one from the firm is under any suspicion for one of the world's biggest ever bank heists.
Mr Dundas accepted arrangements had been ineffective, but did not go into the reasons why. "Whether it was inadequate or whether certain aspects of it weren't carried out as it should have been is still open to review," he said.
PA