Mr David Trimble seems assured of an autumn crisis after the British government's ceasefire definition failed to resolve UUP divisions and saw the First Minister dangerously outflanked by the Conservatives at Westminster.
In Whitehall last night, there was widespread belief that Mr Tony Blair and Dr John Reid had "narrowed the ground" under loyalist and republican paramilitary organisations, serving notice on both that further breaches of their ceasefires would erode public confidence and ensure the probable collapse of the Belfast Agreement.
Indeed, there were signs of nervousness in some sections of the British establishment that the Prime Minister and the Northern Secretary had defined their terms so explicitly.
In separate Commons statements, Mr Blair and Dr Reid signalled that in any future evaluation of the ceasefires, they would give particular weight to substantiated information that a paramilitary organisation was engaged in training, targeting, the acquisition or development of arms or weapons or otherwise engaged in preparations for terrorist activity in Northern Ireland or elsewhere.
In his detailed statement to MPs, Dr Reid said there was "a particular responsibility" on any party participating in the government of Northern Ireland. He would "not hesitate" to use his existing powers to ask the Assembly to consider the exclusion of a party related to a paramilitary organisation deemed in breach of its ceasefire if circumstances required it.
Mr Trimble's supporters believe this threatened use of existing legislation has the potential to fundamentally shift "the blame game" in circumstances of a ceasefire breach which might render his position untenable and lead to a suspension of the Assembly and other institutions.
However he was plainly disappointed at Dr Reid's refusal to concede a new independent element in an "alternative mechanism" for assessing ceasefires.
The Northern Secretary offered an olive branch, in the form of an undertaking to consult about the possibility of inviting some person or persons "to shine a light on levels of paramilitary violence in the community, both loyalist and republican" and to "supplement" the judgments he would make about the ceasefires.
However, even that seemed to shrivel under subsequent exchanges. When pressed by Labour MP Ms Kate Hoey to allow an independent mechanism in the assessments, Dr Reid insisted: "No, I will not abrogate that duty."
While Mr Trimble told him no unionist would give any credibility to any assessment by any Secretary of State, British sources made clear there would be no diminution of Dr Reid's ultimate decision-making powers acting on the advice of his security chiefs.
Mr Trimble's flank appeared further exposed as the Conservative spokesman, Mr Quentin Davies, expressed his "profound disappointment" with Dr Reid's statement, accusing him of "extraordinary vacuousness" and mocking him for bravery only in repeating "words the Prime Minister said four years ago" during the 1998 referendum campaign.
A torrent of complaint from his own benches confirmed the continuing rupture in the Ulster Unionist Party, as Mr Jeffrey Donaldson MP pointed to the near-certainty of a fresh attempt to force a withdrawal from the power-sharing Executive in the autumn.
Disturbingly for Mr Trimble, some pro-agreement unionists joined leading dissidents in rejecting Dr Reid's statement.
Assembly member Mr Fred Cobain said: "Anaemic would be too strong a word for it" while Lord Ken Maginnis declared himself "cynical" about the British government's renewed promises.
Even the Alliance leader, Mr David Ford, said Dr Reid's statement by itself would resolve nothing.
"It is now incumbent on the government to turn these fine words into tough action, otherwise it risks even further damaging its credibility in Northern Ireland," he said.