DURING the 17 months of the IRA ceasefire, Ed O'Brien remained in England, under orders from the IRA, waiting to collect, prime and plant bombs in London.
O'Brien was a classic "sleeper" placed by the IRA's "southern command" in Britain to carry out bomb attacks in city centres, with very little regard for their victims' or their own safety.
He was at the lowest end of the scale. His job was simply to wait for word from his immediate boss to collect and plant a bomb.
One of his accomplices had a simple mechanical job to put together a prefabricated bomb, prime it and put it in a bin or telephone kiosk in central London.
The bomb is designed to offer no intellectual challenges to people like O'Brien. It is like a wooden pencil case. He simply had to slide the lid back, remove a wooden dowel and point a timer switch to one of two times 15 minutes or 20 minutes.
Other IRA figures like O'Brien include Thomas Begley, the Ardoyne teenager chosen to place a similar bomb in the Shankill Road fish shop in October, 1993. He, and 10 innocent people, died when he dropped the bomb.
One of O'Brien's predecessors was Patrick Sheehy, the Limerick man who planted similar bombs around London in the late 1980s. When anti terrorist police raided Sheehy's arms dump in a south London flat, they found he had, left a street artist's sketch of himself.
Sheehy escaped and after a New Year drinking binge in Nenagh, Co Tipperary, he shot himself dead on January 2nd, 1991.
The sleepers are capable of disrupting London's transport system and bringing traffic to a standstill around the city centre. The units are also the cause of most of the indiscriminate bomb deaths in Britain. A similar IRA unit placed a bomb, like the one O'Brien was carrying, which killed the two boys, Tim Parry and Jonathan Ball, in Warrington, in March 1993.
After the IRA ceasefire, it had been hoped that the IRA had stopped recruiting and placing sleepers in Britain. But, last Sunday night, the worst fears of the British police and security services were realised when O'Brien accidentally detonated the bomb on board the No. 171 bus.
O'Brien had gone, to London two years ago, having told his family he was working in Glasgow. He returned to Gorey occasionally to receive cash and fresh orders from the local IRA members who recruited him.
People like O'Brien and Sheehy are the IRA southern command's most direct input into the "armed struggle". The main role of the IRA in the Republic is to supply IRA members in the North with arms and explosives.
O'Brien and Sheehy would be, unsuitable for bomb manufacture and could not be trusted to safely deliver weapons to the Border. They would be unusable in Northern Ireland because of their accents and lack of local knowledge.
Instead, they are given regular sums of cash and sent to Britain to live in cheap rented accommodation and disappear among the tens of thousands of other young Irish men and women seeking employment in Britain.
They are given their own supply of prefabricated bombs and some guns and simply left, waiting to be activated. O'Brien's unit's lite was cut short by the premature explosion on Sunday night. The fear is that the IRA will now simply activate another sleeper unit.
The other bomb squad operating in Britain is made up of some of the IRA's more skilled people.
They construct and plant the type of huge bombs which devastated commercial property at Canary Wharf two weeks ago and, before the ceasefire, in the City of London. This squad operates under the direct control of the IRA leadership and would have no connection with the sleeper units in place in Britain.
The bombs are manufactured in the Border area around north Louth/south Armagh and Monaghan.
Tons of ammonium nitrate fertiliser are ground down to a powder and mixed with icing sugar to make the basic ingredient, known by the acronym ANIS. The mixture is placed in plastic fertiliser bags with loops of Cordex detonating wire.
The detonating wire is connected to a firing unit and, for greater explosive effect, a charge of Semtex is placed among the bags of ANIS.
Up to two tonnes of this mixture was placed in the Ford flat bed lorry stolen in north, Antrim last month and fitted with false number plates and tax disc. Then it was driven north to the Larne ferry port and driven from Stranraer to London.
The security forces fear is that more than one of these bombs was made and is in place, although it is possible that the single large bomb was designed to be a destructive start to a campaign, of smaller bomb attacks by O'Brien and his associates
The Garda and RUC are now desperately trying to find where this bomb squad is working from and who is in it.
The big bombs, known by republicans as "smokies", built by the Border IRA members, caused hundreds of millions of pounds worth of damage to commercial property in the years before the ceasefire.
The reappearance of the big van bomb and O'Brien's death have shown that the southern command of the IRA had remained active virtually throughout the ceasefire period.
If Garda intelligence, is correct, and O'Brien's last visit to Wexford was in December last, then he may have been preparing his work from at least then. The van bomb team must also have been using the period of the ceasefire preparing for operations.
It is clear that the IRA in the Republic is fully reactivated and waging war. The question that still remains unanswered about what is happening in the IRA is whether or not it is prepared to reactivate its "northern command" and begin attacks in Northern Ireland. That would almost certainly be the catalyst to the restart of loyalist violence and a possible descent once more into sectarian conflict in the North.