For a man whose leadership is on the line David Trimble seems remarkably composed. The voice is calm and quiet; the demeanour purposeful, realistic and deadly serious; the peace of his Commons office disturbed only by the sonorous sounds of Big Ben.
The Ulster Unionist leader might well wonder if the bells toll for him. Certainly this is a deadly serious business, with sudden political death a possibility he cannot rule out.
Mr Trimble denies having shifted ground on "the fundamentals", and insists a change in tactics cannot be described as "a colossal U-turn". But he did recently tell his party: "Read my lips. No guns, no government." Does he regret that now?
"We are still on the same position . . . We are not waiving the requirement to decommission. We have gone to a lot of effort to get republicans to acknowledge their obligation to decommission, to have mechanisms in terms of the way in which Gen de Chastelain will operate in place, and, of course, to have the sanction of the action by the governments if it fails to happen."
Obviously he would have loved to have devolution and decommissioning happening simultaneously. But he goes on: "If people are saying `we will do this just starting immediately after devolution', would we be justified in refusing to proceed simply because there is going to be a short delay? We have the process starting, the process of appointing the contact person (the IRA interlocutor to deal with the International Commission) will start on the day of devolution. So while the two processes are not exactly side by side, they overlap and one follows immediately after the other."
Yet Mr Trimble has consistently said he would not sit in government with the representatives of a fully-armed terrorist organisation. Isn't that principle about to be breached?
He insists not. "No, because I said we would not sit in such an administration with people who are fully armed where there was no decommissioning. Nor are we. Because before we go into it they have given commitments on the issue, committed themselves to action on the issue, and we are determined that that action will be followed through. "Therefore the principle that we asserted has been sustained. The timing has moved a little. But again, can anyone erect a change of principle out of a shift of a few days? "
That sounds quite specific. Does he really expect actual decommissioning to have commenced within days of the appointment of the executive?
Not quite, is the answer. Within days of devolution Mr Trimble expects a report from Gen de Chastelain on the "modalities" - which he says will embrace "the questions of amounts, types of weapons, methods of decommissioning." That will leave the issue of timing: "But we expect the general will then outline the arrangements for the next phase of the process and so on."
So is the operative date January 31st? The Ulster Unionist leader insists he does not have "a precise date" in mind. Indeed, he says: "I would discourage people from thinking in terms of a precise date." But for any republican reading this interview, he ventures: "If they commence the legal process on December 2nd, then it would be an entirely wise thing for them to contemplate the beginning of the New Year, the new era, the new millennium, as being an excellent time in which they should do that."
Eight heady days after the Belfast accord was agreed, Mr Trimble famously won the backing of the Ulster Unionist Council with 72 per cent of the vote. Is he anticipating a similar margin this time? And what margin does he actually need to win over doubtful Assembly members?
THERE is a certain inevitability to the answer. The UUP leader is taking nothing for granted and resists an invitation to say 60/40 would be enough. "I know that this issue - because of its sensitivity, because of the emotional impact of dealing with Sinn Fein - is something the members of the council will think very hard about. I see, too, that those who were opposed to the agreement are redoubling their efforts . . . So I take nothing for granted."
But will he resign if defeated tomorrow?
Mr Trimble replies: "I'm not contemplating that, I'm not contemplating failure. I very much expect and hope that we will have an endorsement by the party." He then adds: "Whatever happens, I'm not going to turn my back on the party or this process."
Said with such emphasis, this is clearly important. However, the meaning is not instantly clear. What if his party turns its back on the process? Will he accept a majority verdict against him?
Again the inevitable from a leader in such a position: "I expect and hope that the result will be an endorsement. If it's not that, then we shall have to consider very seriously what we do."
This is important: not least, of course, because some critics think he would not accept defeat as the end of the road. One leading opponent suggests Mr Trimble might do what he calls "a super-Faulkner" - that he might walk away from his party if he thought he had enough strength in the Assembly to save the agreement.
Mr Trimble doesn't much care for this. "You're quite right to say I am persistent. I am. But I'm not another Brian Faulkner, have not been at any point in this process. I have not at any point regarded him as a role model."
So, no possibility of life for David Trimble outside the Ulster Unionist Party then? "As I say, I don't intend to turn my back on the party or on what I'm trying to achieve."
An apology seems appropriate for pressing the point. But it does seem odd that - facing into such a crucial meeting - the leader seems unable to say he will accept the majority will of his party. Odd or not, we have reached the end of the line on this subject, Mr Trimble concluding: "I've a feeling you're trying to draw me into a discussion of what happens if we lose. I'm not contemplating failure."
Laughter follows when I ask whether a narrow win might serve to keep the pressure on Sinn Fein. Mr Trimble has been accused of trying to manage his party on that basis for the past two years. It's "completely false" he says, while confirming he would rather like the comfort of a big majority.
He also takes comfort from the default mechanism outlined by Peter Mandelson, which would see the executive and other institutions suspended should decommissioning not materialise. And Martin McGuinness, he asserts, is "whistling in the wind" in saying there is no such provision in the agreement.
Even so, Mr McGuinness, Mr Martin Ferris and Mr Pat Doherty of Sinn Fein seem to have a common view of what should happen if there is no decommissioning: nothing, save that the institutions proceed. Might Mr Trimble remove the uncertainty by tabling that post-dated letter of resignation mooted in The Irish Times and elsewhere over recent weeks?
The UUP leader specifically dismisses yesterday's renewed press speculation, describing the claim that he would quit if there is no decommissioning by January 31st as "inaccurate". He would, he says, "regard publicly setting a date as wholly counter-productive."
His party's final decision may well rest on what he says to them in the privacy of the Waterfront Hall tomorrow morning. Even if delegates are anxious to trust his new-found faith that republicans will deliver, Mr Trimble still has to answer the question: what happens if that trust proves to have been misplaced?
"I know the concern that exists in the party, indeed in the wider community, about an open-ended process, where you get sucked along and then hung out to dry," he replies. "I know there's an issue there to address. I think actually when people see the outworking of the de Chastelain commission they will see that it is going to be addressed through that. But I'm aware of the concern, and we'll see what we can do about it."
Whatever the precise formulation he has in mind, Mr Trimble's intention seems clear. "It's not open-ended. It's very definitely not. I would say to the party - `Don't worry about having to trust Sinn Fein, or the Irish Government or the British Government. Trust yourselves. This cannot work without the participation of the Ulster Unionist Party.' So, at the end of the day, whatever anyone else might do or say or think, it is our decision . . . we have within ourselves the capacity to put a term to things."
A term to things . . . No leader ever likes to tie his hands. But it sounds as if Mr Trimble is getting ready to do just that. And to tie the hands of those who, come Monday night, expect to partner him in Northern Ireland's new government.