The devil is in the detail. And the detail can be devilishly slow. All afternoon reporters languished outside Castle Buildings, like refugees at a far-flung border post waiting to have their passports stamped.

Some members of the media had been there consistently for the past 16 months, when nothing kept happening with monotonous regularity. Now that we were on the verge of a breakthrough, the normal trickle of news was reduced to a drip.

Nevertheless, the feeling grew that there was movement on the other side of the gates. A Sinn Feiner muttered about the two governments and the Ulster Unionists "passing bits of paper" to one another. Official sources revealed that the plenary had been adjourned from 4 p.m. to 5.30 p.m., which led to a quibble from the media on how you could adjourn a meeting if it hadn't taken place. Official sources stood firm: adjournment it was.

But soothingly we were told that negotiations over the procedural motion were at a "very, very final" stage. Last-minute adjustments were being made and the judgment on the UUP's Mitchell Principles indictment of Sinn Fein would be tied in with the final package.

The evening shadows lengthened. Everyone except the nearby statue of Edward Carson started to wilt. Sinn Feiners and unionists gave "holding interviews" to TV crews. Reporters called their contacts.

There were two schools of thought on what the unionists had done. One interpretation was that they had softened their line on decommissioning. It was now an aspiration, not a demand, sources said.

Another view was that the UUP had secured considerable concessions. It was hinted that the Parades Commission would have its remit widened to include other matters besides Orange marches. For example, it might in future consider the issue of Irish Tricolours flying over the Garvaghy Road and not just Orange feet marching down it. There would be an announcement on this at 6 p.m. Decommissioning had been "parked" but the car could be started again.

Everyone was conscious of the fact that the British Labour Party conference started on Monday; that Tony Blair would be making his conference speech on Tuesday; that Labour had a huge parliamentary majority; and that Mr Blair would not want to have to report continuing intransigence in Northern Ireland to his party delegates.

Thus the pressure on all parties, particularly the unionists, to allow the process to break the decommissioning logjam and move into substantive negotiations by Monday next: two weeks after the target date but just in time for Labour's conference.

But the journalists were not yet in a position to abandon the subjunctive mood: there were "signs" of a major breakthrough; full-scale negotiations "could" start on Monday; "delicate horse-trading" was in progress.

There were hints also about movement on the issue of consent. It seemed the unionists had scored a minor victory. Consent would be a guiding principle of the talks, sources said. In the metaphysics of these negotiations that could be seen as a step forward for the UUP, a setback for Sinn Fein.

The UUP would, it seemed, be able to take part in the process with only minimal contact with Sinn Fein. There would be an occasional plenary, but most of the business would be done on a bilateral or multilateral basis between the parties. The UUP would also have to sit in the same room as "The Shinners" at meetings of the all-important Business Committee, but that could be done on a fairly frosty basis. Remember the rackets and rows at district councils when Sinn Fein started to become a significant presence?

Then 5.30 p.m. came and went. Reporters and camera crews readied themselves for the coming wave of sound-bites. Instead there was an eerie silence. The plenary had been adjourned again, this time until 7 p.m. Nobody was saying why but it seemed as if the UUP might have been just a little too successful: that David Trimble's legal training had scored too many victories in the small print. Sources said there were parts of the revised procedural motion that Sinn Fein would not be able to vote for and that the SDLP was not completely happy with either.

David Trimble came before the cameras. The position on decommissioning was "not ideal" but the issue was not going to be "forgotten, sidelined or buried". He was vague about the reasons for delay. His party had been "fairly comfortable" with the language in the procedural motion but "some difficulties seem to have arisen" and he wasn't quite sure what they were.

W.B. Yeats knew his onions when he wrote that "peace comes dropping slow".