The dreaded "D" word is fast pushing its way back to the top of the North's political agenda. It never really went away, you know. And for all their confident (and genuine) words about more historic days at Stormont, David Trimble and Seamus Mallon are acutely aware that the decommissioning issue has the capacity yet to derail the process.
There is growing anxiety, too, in London and Dublin, although British and Irish officials will not concede that the Belfast Agreement is in serious danger. Ministers and their advisers comfort themselves (with more than a little justification, it must be said) that each and every "insurmountable" hurdle has thus far been cleared. In both capitals there is general certainty about the commitment of Sinn Fein, and the reassuring belief that for the republicans - as for Mr Trimble and the Ulster Unionists - there really is no way back from the Good Friday accord.
So when the First Minister designate says "something will have to happen" to ease his difficulty in sharing executive power with Sinn Fein, there is already instinctive agreement that indeed it obviously will. But at this time of writing nobody seems to have a precise understanding of what Mr Trimble's "something" is; let alone the belief that Sinn Fein can deliver, or that, even if it does, it will be enough to satisfy the Ulster Unionist leader's dissident colleagues.
Too much has been made in recent days of Mr Jeffrey Donaldson's apparent return to the Trimble fold. The Lagan Valley MP faced a difficulty in refusing the opportunity to join a high-powered committee intended to advise Mr Trimble. However, it is clear that Mr Donaldson's position has not changed, and that his apparent rapprochement with his leader is based on the expectation that the Ulster Unionists will not join the Executive with Sinn Fein - even in "shadow" form - without confirmation of prior and ongoing decommissioning of IRA weapons.
Far from being repentant, Mr Donaldson's fellow "young turks" characterise the party as having moved to their man's position. And both governments have been alarmed in recent days by indications from some of Mr Trimble's more dependable colleagues that this is, indeed, a policy position around which the UUP can unite.
It is equally clear that Sinn Fein is not remotely minded, as one party member puts it, "to allow Jeffrey Donaldson to impose now the precondition he failed to achieve" during the final hours of the multi-party negotiations on Good Friday. During his television debate with Mr Ken Maginnis on Monday night, Mr Martin McGuinness again spelt out Sinn Fein's expectation of entry into the Executive as of right, and the determination that unionists would take the blame for any failure to honour the spirit and the letter of the agreement.
The embarrassment for the Ulster Unionist leadership is, as it has always been, that Sinn Fein has it right - and that virtually all the other signatories to the agreement accept that decommissioning is not a precondition for the party's entry into the Executive. The candid acknowledgment that this is so - and the crucial assessment that the Sinn Fein leadership cannot deliver at this stage anyway - has prompted the Progressive Unionists to warn Mr Trimble against digging himself further into a hole.
Like many others, David Ervine and Billy Hutchinson are alarmed by what they see as the propensity of the Ulster Unionist leadership to draw lines in the sand, and the resultant incremental damage to Mr Trimble's credibility when the line is washed away and redrawn.
Senior Ulster Unionists are dismissive of such arguments. They insist that any lack of specificity in the language of the agreement on the decommissioning issue was born of a desire to ease the republican path into democratic politics; that the agreement, like the Mitchell Report before it, commits all parties to the dismantling of paramilitary organisations; and that what might once have been considered a matter for voluntary action by the paramilitary-related parties is in fact obligatory on foot of an agreement endorsed by the people, North and South, in last May's referendums.
They also point to the very clear "linkage" spelt out in the legislation providing for prisoner releases and the requirement that the Secretary of State be satisfied that the organisations in question are co-operating fully with the International Commission tasked to oversee the decommissioning process.
Moreover, Mr Trimble and his colleagues have had some success in establishing, certainly in British minds, that - whatever the precise (or imprecise) requirements spelt out in the agreement - the divided state of unionism and the narrowness of the Assembly arithmetic define the limits of his room for manoeuvre.
Assembly members totally loyal to Mr Trimble have told The Irish Times that should he decide to enter the Executive with Sinn Fein without a start to decommissioning by the IRA, he would fail to carry the Ulster Unionist Party with him. For his part, Mr Trimble has told colleagues (as, apparently, he told Mr Adams during their bilateral meeting last Thursday) that this could be a resignation issue.
So London and Dublin, and Northern Ireland's political leaders, grapple with two conflicting - and seemingly irreconcilable - political realities: the reality of Sinn Fein's expectation of office, without precondition, as spelt out in the Belfast Agreement; and the reality of the continuing threat to Mr Trimble's leadership.
As they search for a solution, both governments have been encouraged by the acknowledgment by leading Sinn Fein figures that, while they intend to hold him to the letter of the agreement, Mr Trimble's is a political problem which has to be addressed. London and Dublin will also be hoping that Mr Trimble and Mr Adams will be able to address it further in the private dialogue which will surely follow from last week's high-profile first encounter. And they are sustained by the core belief that the imperative facing both men - namely, that the agreement survive and prosper - will dictate and define a compromise.
The back of Mr Trimble's internal opposition could plainly be broken by an announcement from Gen John de Chastelain that decommissioning had in fact begun. But if the republican movement continues to resist that course the only other hope would seem to lie in some careful choreography between an agreement between Mr Trimble and Mr Mallon on the shape of the new administration - thus triggering the D'Hondte mechanism and bringing the shadow Executive into play - and an announcement by the general that the paramilitaries have agreed a decommissioning scheme and a timetable for its completion by the May 2000 target date established in the agreement. Given the pressure on Mr Trimble, it would seem at minimum that that scheme would have to guarantee the actual start of decommissioning before the formal transfer of powers to the Assembly next February.
Even then, Mr Trimble might prove unable to deliver. Certainly such a strategy could provoke a final showdown with Mr Donaldson and the other dissidents. Without doubt it would represent Mr Trimble's greatest gamble with his own constituency. For here's the point: unionists see the retention of private armies as the retention of the threat that, should politics disappoint, the IRA might indeed to go back to doing what it has previously done best. They took at face value Mr Tony Blair's assurance that the test for those new to democracy would necessarily become more rigorous over time. They expect decommissioning to happen. And they are not yet convinced that Sinn Fein, the SDLP and the Irish Government have accepted that reality.
