Deadlines were made to be broken. That is the one lesson everyone has learnt from the peace process. Does anyone now remember Tony Blair's "absolute" deadline for devolution as June 30th last year? Pregnant with grim foreboding, that dread date slipped past almost unnoticed in the end. The parties failed to reach agreement but dire warnings about stopping Assembly members' salaries were never implemented.
Deadlines in the peace process are like those spots on the wall that paramilitaries focused on when they were arrested: nothing more than an aid to concentration.
The first sign of trouble yesterday came with reports that Mr Trimble had turned up late for a 10 a.m. meeting with his Assembly party. There was very little ballyhoo and nobody even knew for sure the meeting was taking place until a few Assembly members casually confirmed it to the waiting media. Like a lot of unionist gatherings, you were left wondering when a meeting is really a meeting. It was said that Mr Trimble had merely taken "soundings" from his party colleagues.
The only consistent note to be heard was that Trimble wanted to "go for it". There was much talk of the UUP leader's "gut feeling" that the Hillsborough deal, as clarified in the past week, was worth accepting.
But had he got the numbers? There was a growing suspicion that he did not. The word from the resurgent No camp in the party was that those who were "nervous" at last November's UUC meeting had turned into rejectionists; many who had been Yes voters all along had now become "nervous". Estimates flew around Stormont: Trimble would lose by 60-40 or even 70-30.
It might help readers in the Republic to compare what is happening in unionism with the difficulties the two major Civil War parties had over many years in accepting divorce and contraception. A one-party state - what Edward Carson called "the Protestant province of Ulster" - is turning into a society where equality between two traditions is being institutionalised, with a panoply of laws, agencies and procedures to ensure, as far as humanly possible, nobody is ever again discriminated against politically, socially or economically because of their religion.
It is a huge cultural change which the sturdy farmers and shopkeepers of the Ulster Unionist Council are being asked to facilitate. Small wonder that they have been given pause for thought. Should they choose to stand in the way of Northern Ireland's cultural revolution, they may very well be swept aside. Share power and give full recognition to your neighbours, or Dublin's role as guarantor of nationalist rights will have to be enhanced: joint authority is the unspoken threat underlying the current process.
David Trimble is now the Willy Loman of Northern Ireland politics. The hero of Arthur Miller's Death of a Salesman had little more than "a smile and a shoeshine", but Mr Trimble will have to persuade his party that he has something much more substantial. He has the promises of two sovereign governments and certain commitments from the IRA. But nothing is certain in life except the proverbial death and taxes and there is inevitably a leap of faith involved for unionists who decide to back this deal.
Already Mr Jeffrey Donaldson has poured scorn on the Hillsborough package. Denouncing it as a "phoney process" he dismissed the pledges from Mr Blair as devalued currency and posed the rhetorical question: "Have the IRA [as distinct from Mr Blair] clarified what they mean by putting guns beyond use?"
As part of his "hot gospel" campaign for the Hillsborough deal, it seems unavoidable for Mr Trimble to attack his opponents very directly. Mr Donaldson has made himself the obvious target, much more than the Democratic Unionists who are regarded with distaste even by anti-agreement members of the UUP. The first sign that this is genuinely a battle royal will come when Mr Trimble takes on his chief critic and main rival for the party leadership. Mr Donaldson is no seven-stone political weakling and would doubtless respond in kind: the media will readily hold their coats.
Naturally there will be suspicion on the nationalist and republican side that the UUP leadership is merely seeking to squeeze even more concessions out of London, with Dublin sighing and rolling its eyes to heaven. The renewed emphasis on decommissioning and Mr Trimble's insistence that putting weapons beyond use implies decommissioning will generate unease in republican circles, where it was hoped that the last had been heard of the D-word. But Mr Martin McGuinness was taking a positive and pragmatic approach last night, accentuating the positive factor of Trimble's support for the deal rather than dwelling on the potentially alarming fact that tomorrow's meeting had been rescheduled.
It is hard to quibble with Mr Mandelson that he would "rather wait a week for a good result than rush forward now". His appeal to nationalists and republicans to appreciate the need for a breathing space will be listened to sympathetically, on condition that Mr Trimble gets out there with his suitcase of political concessions and his shoeshine and starts knocking on doors from Killinchy to Kinawley.
The euphoria in the pro-agreement camp generated in the immediate aftermath of the Hillsborough deal had well and truly evaporated by the middle of this week. The dripfeed of concessions to Trimble was generating nationalist unease and the SDLP and Sinn Fein were competing vigorously with each other in their opposition to the watering-down of the Patten report.
A little of the post-Hillsborough mood has been recaptured following Mr Trimble's public espousal of the package. Mr Sean Farren of the SDLP said last night he trusted there would now be an end to the process of seeking concessions from London and the focus would be exclusively on winning the UUC around.
However long it may last, there is again a little of that cross-party, cross-community drive for change in the air. We have not seen it since the days leading up to the 1998 referendum, and then only after the U2 concert when middle-aged rockers Hume and Trimble held hands for a Yes vote. Mr Trimble will need to keep up the momentum between now and May 27th: one way or the other, the future of Ulster Unionism may be decided in the coming week.