Cops were forced to pay old informants to return to work after the infamous Northern Bank robbery. In the security panic that engulfed the force after the huge £26m heist, officers from the elite C3 made contact with republican agents sacked earlier that year and offered them their jobs back.

But several refused and demanded cash payments before they would come back into the intelligence net.

Some did tell their new handlers that they had been aware that a major event was planned by the IRA before Christmas and it’s understood that two of the sacked agents named IRA men who were involved in holding the families of the two bank workers hostage.

Said a source: “One said he saw a couple of IRA men he knew the day before the robbery was carried out with their heads shaved and their eyebrows shaved and knew that they had been picked to do something big.

“Another former agent confirmed this and identified the same men with their eyebrows and heads shaved to ensure no hair follicle was left at the hostage scenes that could link them to the crime.”

The former agents had been dumped months before the robbery following a review of registered informants by the PSNI’s then head of Crime Operations Sam Kincaid.

His successor Assistant Chief Constable Peter Sheridan — now also retired — told a Policing Board meeting in Enniskillen in June 2006 that a reassessment of informants started in the summer of 2004 had ultimately led to 24% of informants recruited by the RUC being discarded.

He said the review led to the dumping of some informants who were involved in criminal activity, established new procedures to deal with informants suspected of committing serious crimes and created a new unit called the Central Authorisation Bureau to oversee all permits for covert policing operations.

The biggest puzzle arising out of the intelligence debacle was that none of the high level intelligence agents close to the IRA’s Army Council ever gave any hint that the robbery was being planned.