The "modalities" for disposing of arms were agreed with representatives of the three main paramilitary groups at the decommissioning sub-committee at the Stormont talks over a year ago.

According to some of those taking part there has been, for several months, a clearly worked-out set of arrangements under which arms can be handed over and disposed of.

From the outset both governments agreed that decommissioning would take place in an environment which assured the paramilitaries that the people delivering the weapons would have immunity and that there would be no forensic examination of guns.

Legislation, in the form of Decommissioning Acts, was put in place in both jurisdictions.

The legislation gives statutory authority to the Independent International Commission on Decommissioning, which has offices at Dublin Castle and at Rosepark House, near Stormont in east Belfast. Gen John de Chastelain is the head of the commission.

Mr Donald C. Johnson is in charge of the Dublin office and will probably assume charge of the decommissioning of any republican arms.

Brig Tauno Nieminen, of the Finnish army, will have control of the nuts-and-bolts part of taking in the arms and destroying them.

Explosives in the North will probably be taken to the British army base on the Co Down coast at Ballykinlar. In the Republic, the IRA has up to three tonnes of Semtex plastic explosive hidden in bunkers. This is likely to be taken to the Curragh Camp to be disposed of by one of the Army's Explosive Ordnance Disposal (EOD) teams.

The explosives will simply be placed in a hole in the ground in a wide expanse of land and detonated. Given the power of Semtex - a couple of pounds could demolish an average-sized house - it will probably take several operations to dispose of the entire IRA stock.

Security sources on both sides of the Border are most concerned that explosives are handed over. Plastic explosive is used in entirely offensive (as opposed to defensive) terrorist acts such as booby-trap bombs and mortars and for boosting the huge car bombs which the IRA has used in Britain since the early 1990s.

The IRA cannot insist that Semtex has any "defensive" use as, say, in the protection of Catholic communities against assault by loyalists, as happened in the late 1960s and early 1970s.

Dealing with rifles, handguns and improvised or home-made weapons is relatively simple. Ballistic sections in both the Garda Siochana and the RUC have been doing this throughout the Troubles.

Guns can be destroyed in various ways by having their barrels bored or mangled. This can take place either at military camps or, if small numbers of weapons are involved, at the RUC or Garda ballistics sections.

The legislation in both jurisdictions means that once decommissioning operations are in train the paramilitaries handing over arms are immune from prosecution while the arms are in transit to the agreed sites for destruction.

The paramilitaries have already been given code words which they can use if stopped by the security forces while transporting the weapons for destruction.

The paramilitaries also have to appoint nominees through which the Independent Commission will work. The Ulster Volunteer Force (UVF) has appointed Billy Hutchinson, a former UVF prisoner who represents the Progressive Unionist Party (the UVF's political wing) in the Shankill Road area.

The IRA and the other loyalist paramilitary organisation, the Ulster Defence Association (UDA), have not yet put forward nominees to deal with the Independent Commission.

It is understood that the IRA does not intend to decommission any of its weapons in the immediate future, probably not this year.

In a statement at the end of April in which it, more or less, endorsed the Belfast Agreement, the IRA added: "Let us make it clear that there will be no decommissioning by the IRA. The issue, as with any other matter affecting the IRA, its functions and objectives is a matter only for the IRA, to be decided upon and pronounced upon by us."

Despite the belligerent sentiment inherent in this statement, security sources believe the IRA leadership has accepted that it cannot return to any offensive military operations without suffering severe setbacks. If it returned to its campaign of violence, both governments would rearrest the prisoners it had released early and Sinn Fein, as the IRA's political wing, would again face international ostracism.

It is not clear why the UDA has not appointed a nominee. It is thought that the association does not have a clear system of central control, but is rather a federation of local "brigades". It is thought possible that the UDA may have some difficulties in appointing a single nominee who is acceptable to the entire organisation.