David McKittrick: One reason to expect fresh agreement: Ulster's politicians all love the assembly

Opinion in the Stormont canteen is that the three most effective ministers are a former IRA commander and two Paisleyites

Tony Blair said "Good morning" to the media when he emerged from Hillsborough Castle yesterday following his marathon talks involving the Irish government and the local parties. He used that greeting because it was after midnight as he made his way, hunched against the chilly March drizzle, to report on the outcome of 30 hours of negotiation. It was a pretty miserable scene.

He and Bertie Ahern had arrived on Monday with a 28-page document covering most of the most difficult issues: how to get the suspended assembly up and running again, how to get the IRA to cease its activities, what to do about policing and so on. The two prime ministers spoke of significant progress being made, but there was no sense of celebration. All the issues had been aired with the parties but, after 30 hours, the bottom line was that nobody had signed up for anything. The assembly elections scheduled for 1 May had been postponed for four weeks to allow everybody to digest the document, said Blair.

Things had seemed to be going reasonably well in the talks until teatime on Tuesday, when Sinn Fein reacted angrily to the proposal that sanctions could be used against the party as punishment for IRA misdeeds. Then the Ulster Unionist leader David Trimble walked out of Hillsborough, his aides saying he had business to attend to in London. This left Tony Blair, who himself had plenty of business to attend to in London, stuck in Hillsborough without one of the most important participants in the negotiation.

At that point some feared the worst: there were rumours that it was all falling apart and could end in fiasco. One person who met Blair and Ahern in the late evening summed up their prime ministerial dispositions as "knackered and pissed off". But the two kept the show on the road, at least enough to be able to claim that progress had been made, and that more would follow in the coming months. It might well be wondered how any breakthrough can be expected against such an unpromising background.

The fact is though that powerful influences are propelling most of those involved towards a deal. Almost uniquely in the politics of Northern Ireland, the usual unhelpful centrifugal forces may be outweighed by new centripetal factors. This was best illustrated a month ago at another very different political scene, this time in the sumptuously gilded surroundings of the Stormont Assembly's Long Gallery.

On that occasion, assembly members, coffees and canapés in hand, gathered for the unveiling of a unique group portrait by the Belfast artist Noel Murphy of all the 108 assembly members, the brainchild of journalist Eamonn Mallie. There is little friendship and less trust among the various political parties, but opponents and rivals surged forward in fascination to see how the artist had captured on a single canvas not only themselves but figures such as David Trimble, Gerry Adams, John Hume and Ian Paisley. Here were most of the political classes in one room, and if there was not exactly harmony among them, there was a very marked sense of common purpose. With only a handful of exceptions these people like and value the assembly, and they want it back in operation again.

Some assembly members are colourless, some have few political talents and are frankly a waste of space, some see it as simply a forum for venting prejudice, some are pompous, some are venal; for some it is just a high-status, well-paid job. But others are hard-working, dedicated, good at their jobs and have a marked sense of duty. One of the major political faultlines is whether parties and individuals are for or against the 1998 Good Friday Agreement, yet membership of the assembly transcends even that fissure.

Nationalists and republicans are enthusiastically pro-agreement; Mr Paisley's Democratic Unionists are dead set against it; David Trimble's party contains both sections of opinion. The assembly was created by the agreement, but even anti-agreement people prize it, generally seeing it as being in both their political and personal interests. It is viewed as something close enough to a level playing field for the business of politics.

Sinn Fein used to be totally anti-assembly, but this proved to be a tactical position quickly abandoned once it was established. Opinion in the Stormont canteen has it that the three most effective ministers have been Martin McGuinness, Peter Robinson and Nigel Dodds – a former IRA commander and two Paisleyites. Republican enthusiasm for the assembly has grown so much that, in one of the many political inversions of recent years, both Sinn Fein representatives and their grass roots are much keener to restore devolution than many Protestants and Unionists.

Much of the Unionist grass roots either dislikes devolution or is largely indifferent towards it. This is obviously a drawback for devolutionists, though it is balanced by the fact that the Unionist political class is so heavily in favour of the assembly.

This pro-assembly consensus among the leading figures of all the major parties represents the strongest reason for calculating that, for all its problems, the current wearying round of negotiations will eventually succeed. In other words, there will probably be a breakthrough because nearly everybody wants one, because it is the only way to bring the assembly back.

Blair and Ahern did not achieve a final breakthrough this week, and nor did they guarantee success, but they laid the groundwork. A large measure of agreement was achieved on issues such as policing that have for years seemed insoluble. The sanctions issue was not cracked, but there is a fair chance that Sinn Fein and the IRA will see it as one unwelcome part of an otherwise acceptable deal. It may help that the governments are prepared to extract it from the main package and present it as a free-standing intergovernmental move.

The package is to be published in a month, and if all goes well, the IRA will respond with an "act of completion" that will involve arms decommissioning. The IRA must also, in the Government's words, "cease activity in all its forms". After that there will be assembly elections at the end of May. The result of those elections could be pivotal, since the four main parties are all close together in terms of support. The DUP is pushing hard to dislodge the Ulster Unionists as the largest Unionist grouping in the assembly, while Sinn Fein is ambitious to become the main nationalist party. Since no one has ever been able to predict Northern Ireland elections, the results will be a real roll of the dice.

One striking point in all of this is that such negotiations used to be regarded as matters of war and peace. This time it is different; they are now viewed as likely to end either in breakthrough or impasse.

It is a measure of how much the peace process has delivered that it is more and more in the political sphere, and less and less a matter of life and death. Blair and Ahern may thus conclude that those hours of being knackered and pissed off will ultimately be worthwhile.