Could London (and Dublin) have decided that David Trimble's survival is no longer material to the future of the peace process?

At a glance the question will strike the British Prime Minister, Mr Blair, and the Taoiseach, Mr Ahern, as manifestly absurd. They have made a colossal commitment to the creation and, so far, successful implementation of the Belfast Agreement. Its guiding principle is consent; its purpose a balanced, settled constitutional dispensation governing relationships within Northern Ireland, between North and South and within these islands as a whole.

As recently as Friday in this newspaper Mr Peter Mandelson said the two governments were the guardians of the new institutions, and that he would not shirk the responsibility placed on him should the IRA fail to honour its side of the Mitchell bargain. While Mr Mandelson conspicuously declined to confirm Mr Trimble's very precise deadline for a start to IRA decommissioning, the Northern Ireland Office line has been that, if the Provisionals do not deliver, Mr Trimble will not be left standing alone.

The meaning of all this was spelt out at the conclusion of the Mitchell review. Mr Mandelson repeated it here on Friday. In the event of default, either on devolution or decommissioning, the two governments would suspend the institutions established under the agreement.

Hence the widespread assumption that, if the republican leadership maintains its present public position - that Mr Trimble's is a unilateral deadline outside the terms of the Mitchell review - London will be reinstating "temporary" direct rule somewhere between January 31st and February 12th.

Such is their certainty about this that last week's meeting of the UUP's Assembly party was dominated by consideration of what will happen post-suspension of the Executive. Their expectation will have been reinforced by Mr Mandelson's assertion, echoing that of Mr Trimble, that it is on this month's report by the Decommissioning Commission, and not next month's reconvened meeting of the Ulster Unionist Council, that everything will turn.

For all that, the dark fearful question about British (and Irish) intent is exercising some of the most senior and serious members of Northern Ireland's putative new establishment.

They know all the comforting words of reassurance. But they have been here before. They also know something of the near-inescapable balance of pressure within this process. It was confirmed by an Irish source last summer, at the height of the ultimately doomed race to meet Mr Blair's June 30th deadline.

"There is an inevitability about all this," the source confided: "The two governments will push the Provos as far as they can. But if they refuse to yield, the squeeze invariably comes back on the other parties."

Might Mr Trimble be about to feel the squeeze one more time? Neither government would admit such intent or inclination, while time remains for the IRA to do something, to make some gesture. Despite all indications to the contrary, indeed, some key players in Dublin and London believe they will bite on the bullet.

However, the IRA would be running entirely true to form should it refuse. And if it does? Suppose Gen de Chastelain is forced to report that - for reasons of internal management, rather than any dark political design - the IRA is unable to move at this stage? But suppose, in addition, the general feels able to express full confidence that it is the republican intention to have met the agreement's decommissioning requirements come May?

There is never any shortage of language to convey the impression of movement. Mr Mandelson says the general's report will inform his judgment. It is not hard to imagine a report which, while falling short of an actual start to disarmament, might otherwise satisfy Mr Mandelson's determination that it should be "positive" and "encouraging".

Given a strong promise of decommissioning in May, is it really conceivable that Mr Trimble would pull the plug on the fledging institutions? Mr Gerry Adams says not. And it may well be equally inconceivable to those in London and Dublin who, in truth, think decommissioning crucial largely because the unionists have made such a fetish of it. Moreover Mr Trimble is not, as even one of his admirers puts it, "a man known for drawing lines in the sand".

Yet he has on this occasion, and the post-dated letter of resignation has been fortified by the events of the past week.

Nationalist Ireland watched contentedly on Wednesday as Mr Mandelson took on the combined forces of unionism and faced them down. Spitting fury, Mr Trimble told Mr Blair that the decision to scrap the RUC's royal title dishonoured the British government. It was a bitter moment for Mr Trimble - no less so for its terrible predictability.

Having arguably misjudged and mishandled the issue from the outset, Mr Trimble had continued to battle almost exclusively on the symbolism. On Wednesday he went to the Commons to face the cold reality of defeat - a defeat, moreover, delivered by the man he had expressly asked should replace Mo Mowlam.

Neither Mr Mandelson, Mr Blair or Mr Ahern should underestimate the impact of that defeat on Mr Trimble's party supporters or the wider unionist constituency, or its implications for what might happen next.

Whatever the wisdom or necessity of Mr Mandelson's decisions, unionism operates by its own realpolitik. Some anti-agreement campaigners believe the RUC has replaced decommissioning as the issue that could seal Mr Trimble's fate at the UUC on February 12th. His supporters and well-wishers are left asking themselves - why now?

How and why did Mr Mandelson decide that it made political sense to pronounce on Patten "before time", without any start to IRA decommissioning, and just weeks ahead of Mr Trimble's resumed date with destiny?

One of those asking these dark questions this weekend ranks among the most shrewd, most sober observers of the Northern Ireland game. He has played an important role - largely behind the scenes - in bringing the agreement this far.

He knows Mr Mandelson is no fool. He hopes (and almost believes) that the Secretary of State - a deeply suspicious man - can have decided to move ahead on Patten only in certain expectation of IRA delivery.

Almost believes. But if there is no prior Mandelson-IRA deal on decommissioning, he says, then the implications could be profound: "It would suggest to me that they have decided David Trimble's survival is immaterial. The loyalists could split and the whole edifice collapse, leaving Sinn Fein free to push for joint authority. Are Mandelson, Blair and Ahern really prepared to hang Trimble out to dry and see that happen? That's really the question for me."

Mr Trimble, meanwhile, expects his answer in just seven days. He and his electorate need to know that it is London and Dublin who remain in control of this process.