Some who are now dissidents were Provisionals when Donaldson was informing in the 1980s and '90s, so he could have personally betrayed them.

If dissidents were responsible, it would make sense to claim the killing because of its popularity with republican grassroots.

Although, they may have decided not to because keeping the Provos in the frame causes Sinn Fein political problems.

But sources close to RIRA and CIRA say Denis Donaldson alive was an embarrassment to the Provos and great propaganda for the splinter groups. Apart from minor incidents, both groups are largely inactive.

THE BRITS The British security services are morally capable of killing an informer. Once agents outlive their usefulness, the state has no scruples. "It's entirely possible they brought in killers who themselves could be found dead from 'an overdose' soon, " says exintelligence officer Martin Ingram.

The British track record includes colluding in the death of Pat Finucane and others. However, Donaldson presented no major threat to them. He wasn't about to write a book exposing British dirty tricks. He just wanted to live quietly in Donegal.

'FREELANCE' REPUBLICANS Donaldson could have been killed by someone with a personal vendetta. Dozens who were jailed, or whose relatives were killed or imprisoned, could blame him.

After reading of his whereabouts in the newspapers, someone could easily obtain a shotgun and take revenge.

But there's no tradition of such unauthorised acts in the Troubles. The killers may have been aiming to create the impression it was more amateurish than it was.

Shotguns are as lethal as normal paramilitary weapon at close quarters and can be virtually forensically untraceable.

Donaldson's family visited the cottage but the killers knew he was alone and that they'd be undetected by gardai. It was more professional than it initially appeared.

ROGUE IRA ELEMENTS The seizure of assets along the border by CAB is said to have angered Slab Murphy's supporters who believe the Sinn Fein leadership gave promises this wouldn't happen. These border republicans then embarrassed Sinn Fein 48 hours before the Blair/Ahern visit and damaged the initiative.

IRA informer Eamon Collins, who gave evidence against Slab in a libel case was later killed. However, word of border discontent is speculative. It remains to be seen whether CAB's move against Murphy is tokenistic or a serious crackdown.

THE IRA ARMY COUNCIL After the Northern Bank robbery and Robert McCartney's murder, killing Donaldson would be too big a risk for the Army Council. On the eve of the governments' initiative, the timing was disastrous for Sinn Fein.

Or was it? Better to murder before the Assembly returns in May. Realistically, there won't be a political deal until next year, by which time Donaldson's killing will have long dropped from the agenda.

The IRA statement denying involvement notably used the word "death" not "murder".

The Provos have lied time and time again about Colombia, Garda Jerry McCabe, and countless other incidents.

Donaldson's continued existence incensed ordinary IRA members. Gerry Adams unwittingly posed for photographs with him a week before he was outed. "Gerry was made a fool of and the IRA leadership didn't like that, " says a source.

While Sinn Fein leaders were genuinely stunned when Donaldson was outed, their body language and words suggested a more calm and organised response this time.

The two governments appear to have accepted PIRA's denial and the peace process won't suffer long-term damage.

'One of the most far-reaching and squalid scandals in the history of the Belfast IRA' "JOE Fenton came under suspicion when the leadership first began shipping the Libyan weapons to the Northern ASUs [Active Service Units]. A number of consignments headed for Belfast were mysteriously intercepted by the RUC, and it was obvious that an informer was at his or her work. The common link in all the losses was Fenton, who turned out to have been directly or indirectly involved in the purchase of the vehicles used to transport weapons from southern dumps.

Eventually, in February 1989, and only after he had fled to England but then inexplicably returned, Fenton was arrested by the IRA's security unit, the specialised team whose job it was to ferret out informers from the ranks of the IRA, interrogate them, and, if it found them guilty, shoot them dead. What happened after Fenton's arrest has taken its place in republican legend as one of the most far-reaching and squalid scandals in the history of the Belfast IRA.

Fenton was abducted by the security unit and held for interrogation in a house in Andersonstown, west Belfast, but after only two days he was taken out and shot dead. His body, with a single bullet wound to the head, the IRA's customary punishment for those caught informing, was dumped in an alleyway in nearby Lenadoon.

The speed with which Fenton was killed caused a major row within the IRA.

An informer as important as Fenton should have been taken away for lengthy interrogation and debriefing so that the damage he had done could be assessed."