The RUC is dead, long live the Police Service of Northern Ireland. In stark summary, that was the message from London to the people of the North this week. There has been pain and a sense of betrayal on the unionist side and a cautious welcome, accompanied by rising expectations, on the part of nationalists.

The announcement carried echoes of the decision to launch a new Bloody Sunday inquiry, although the ripples will spread wider and last longer. What did you expect, was the message from Mr Chris Patten when he released his commission's report in September. The terms of the agreement negotiated between unionists and nationalists did not leave either Mr Patten or the British government much room to manoeuvre, had they so desired. And as the Northern Secretary suggested in his speech to the House of Commons this week, a nine to one differential between Protestants and Catholics in the police was not sustainable when the population was at least 40 per cent Catholic.

It was a battle Mr David Trimble could not win but this has not protected him from heavy criticism for failing to save the name and the badge.

The dilemma here was that nationalists would not join a police force in significant numbers unless it had a comparatively neutral name and insignia. In an ideal world the UUP could have seized the high moral ground by advocating the pluralist approach hinted at in the past by the First Minister. But that would have been political suicide and the best unionist leaders can do is to tell their followers: "I feel your pain."

The UUP dissidents have seized on the police issue to stoke-up their campaign against the agreement and by implication Mr Trimble's leadership. Signatures are being sent to the chairman of the UUP executive, Lord Rogan, calling for a special meeting of the 110-member party executive to discuss policing. A total of 25 signatures are required and if the dissidents can achieve this, they hope the special meeting can take place before the February 12th gathering of the Ulster Unionist Council.

These are dangerous times for the UUP leader and consequently for the peace process although, as dissident sources wryly remarked: "The only thing David Trimble will defend to the hilt is his own position."

The upbeat mood after this week's encounter between the Taoiseach and the UUP leader does not seem to have been based on the expectation that guns and explosives will be destroyed by the end of this month. There is a quite remarkable rapport between Mr Ahern and Mr Trimble. Unionists are also believed to have a high regard for the Taoiseach's senior civil servants for the manner in which, during the fraught Good Friday negotiations, they articulated the relationship between the North-South bodies and the Northern Ireland Assembly. All eyes once again focus on Gen de Chastelain and the report he is due to release by the end of the month. The general has been meeting the IRA and is also in receipt of the best advice and counsel the two governments can provide.

Senior sources have not given up hope that the IRA will stage an "event". Even the idea of simulated decommissioning - a "dummy run" - has been floated but republican sources greeted it with incredulity. Republicans point out that there is no January deadline in the Belfast Agreement. While most observers accept that Mr Trimble had to propose a reconvened meeting of the UUC to save his political skin, republicans regarded this as a breach of faith. The implication from what the IRA said subsequently was that the agreement reached in the Mitchell Review almost came off the table.

Happily for the peace process, the IRA interlocutor was not withdrawn. Such a move could have precipitated a major crisis. The hope now among supporters of the peace process is that the general will at least be able to report that, whereas no guns have been destroyed, there is a basis for confidence that the May deadline for complete disarmament can be met.

Expectations remain that the general's report will be positive, perhaps even upbeat. But in the absence of guns going through the grinder, Mr Trimble may not be able to get through the UUC meeting on February 12th. If that day goes badly for him, it could cause terminal damage to the process. It will be absolutely essential to gauge the mood of unionism with complete accuracy around this time.

There is a lot of hurt over the Patten report but, in time, unionists may reflect that the same officers are still donning the same uniforms and heading out to cover the same beat every day and that the proposed changes are being brought in gradually over a fairly lengthy period. Is it worth risking the collapse of the IRA ceasefire and a return to bombing and shooting just for a badge and a name?

If unionist anger is such that Mr Trimble's political survival cannot be guaranteed and if the general's report is insufficiently positive, there could be an immediate move to suspend the agreement and initiate another review but possibly with the Executive continuing in shadow form.

It is axiomatic on the part of senior unionist sources that Mr Trimble cannot continue as First Minister without a decommissioning event this month. But if he resigned he would have great difficulty getting re-elected under Assembly rules. To avoid a repetition of the farce over Mr Seamus Mallon's position as Deputy First Minister, it would be necessary to suspend the institutions. Once the review was successfully completed, the light-switch could be thrown again and Mr Trimble resume his position without a vote.

All very neat and tidy until you consider the state of feeling on the republican side. A suspension of the institutions, with Martin McGuinness and Bairbre de Brun losing their newly acquired portfolios and, in particular, the removal of powers from the North-South Ministerial Council, would provoke widespread anger and have the potential to cause what senior republicans call a "debacle".

Dublin was quick to deploy its diplomatic and political skills and resources to reassure the unionist leadership at this very difficult time. The measured words of Mr Jeffrey Donaldson this week have also been noted; Mr John Taylor's prediction of an imminent return to direct rule has reportedly driven some of his colleagues to distraction although the UUP deputy leader has a history of coming down on the side of the angels eventually.

Ironically, it seems Dublin is Mr Trimble's best hope but the Taoiseach will have to handle the republican constituency with care. It was noticeable that his comments on decommissioning after the Trimble meeting were more restrained than his remarks in South Africa. Unionists hoped he would repeat the strong words he used in Johannesburg but Mr Ahern was no doubt aware that this could have stirred up a republican hornets' nest.

Comments by republican leaders in coming days will be noted with great interest. Can they live with another review, possibly chaired by Senator Mitchell or, alternatively, by Mr Mandelson and Mr David Andrews? It is difficult to imagine them welcoming the prospect. Do republicans accept that Mr Trimble's survival equates with the continuance of the process? Can Mr Adams and Mr McGuinness predict a united Ireland in the US only to return home and find the pause button pressed on their party's place in government?