Northern Ireland politics is a series of double-acts: Hume-Adams, Adams-McGuinness, Trimble-Mallon and now Hume-Trimble. The two men have been brought together by the Nobel Peace Prize committee but it is very much a case of "for one night only".

Trimble's long-term political partner is Seamus Mallon, since Hume decided not to go for the post of Deputy First Minister. Besides, although Hume is only seven years older than Trimble, they are at very different stages of their political career.

For Hume, the Nobel award comes as the crowning achievement of a 30-year odyssey during which he doggedly and consistently pursued his aim of remedying the grievances of the nationalist community by non-violent means. The Derryman made clear recently that he has no intention of leaving the political stage but, of necessity, the main spotlight will be on Mallon rather than Hume from now on.

Trimble has been around for a long time but his image until recently was that of an abrasive hardliner, a former member of the ultra-unionist Vanguard organisation who celebrated an Orange "victory" at the Garvaghy Road in 1995.

Trimble came to the leadership with the support of hardline elements in the Ulster Unionist Party. But although he started out on the fringes, he quickly began to move to the centre.

With the IRA ceasefire in 1994, everything changed. Trimble read the writing on the wall: protest politics and the "No-no-no" approach of the past had failed to bring down the Anglo-Irish Agreement; the establishment of a powerful pan-nationalist front faced unionism with a dangerous new challenge; the strategy of turning what one senior unionist called a "stone face" to change was no longer a viable option.

The Nobel citation expressed it rather well: Hume was praised for being "the clearest and most consistent" in his work for a peaceful solution; Trimble received marks for his "great political courage . . . at a critical stage of the process".

The citation noted that Trimble, "as the head of the Northern Ireland government" had taken the "first steps towards building up the mutual confidence on which lasting peace must be based".

In fact, as he himself stressed recently, he is only "First Minister-designate". The Assembly which elected him exists in shadow form and, according to most readings of the agreement, will not be given any real powers unless an executive is established which includes Sinn Fein.

Trimble of course insists he will not participate in the formation of an executive unless there is some form of prior IRA decommissioning. Republican sources declare that the IRA has not the slightest intention of meeting his demand.

Some observers say the Nobel award will strengthen Trimble's resolve to hold out for decommissioning. Others believe it will render his position more difficult.

The fundamental point about decommissioning at the end of the day is that it is a voluntary gesture. The IRA has held out in the past and shows every sign of doing so once more, on this occasion.

Therefore, the more likely result of becoming a Nobel laureate will be to make it harder for Mr Trimble to resist Sinn Fein membership of the Northern Ireland government. Picture the scene at the awards ceremony in Oslo on December 10th: Hume and Trimble are being feted and feasted but the world's media want to know when the annoying wrinkle of decommissioning is going to be ironed out. When Trimble replies that it's up to the IRA, the world's media may well respond that "The IRA is on ceasefire so what is the problem?"

Of course it may all be resolved before then. Mr Trimble touches down in Belfast this morning and his phone will soon be ringing with statesmen and senior officials wanting to discuss the weapons impasse. Meanwhile, Sinn Fein's Mr Martin McGuinness is scheduled to meet Mr Blair at Downing Street in the next few days.

The Ulster Unionist conference takes place in Derry next Saturday and already the indications are that dissent will be minimal. The Union First group says it has declined the offer of a fringe meeting in the conference hotel because the 9.15 to 10 a.m. time-slot was not suitable. It may hold a dissidents' gathering in Belfast the previous evening.

COLOUR-writers will lament the absence of Mr John Taylor at a family wedding. The man widely seen as the alternative leader, Mr Jeffrey Donaldson, will be in the US, where he is taking over from Mr Trimble on the industrial promotion tour. One UUP dissident said he might not even attend the conference because, in his view, the occasion will be well choreographed and opportunities for criticising the leadership and its policies likely to be limited.

A Trimble triumph would appear to be on the cards, but with little in the way of comfort for nationalists on decommissioning. If that is to come, it will be much later, after a great deal of hard talking and the burning of several gallons of midnight oil.

At a deeper level, the effect of the award on the unionist community in general could be interesting. Nationalists and republicans have been "adopted" internationally almost from the beginning of the Troubles, giving rise to the waggish acronym of "MOPE" for Most Oppressed People Ever. Unionists, on the other hand, have never been world darlings and have generally found themselves lumped with the Afrikaners and Israelis as a distinctly untrendy community under siege.

The effect on the unionist community of being embraced by the world and given its most prestigious accolade will therefore be worth watching. For republicans, meanwhile, it is Brave Face Time. It will gall them particularly to hear David Trimble's "courage" being praised while not a word is said about the bravery of their own political leaders. Republicans would doubtless argue that it took a lot more guts for Sinn Fein leaders to face down the quarter-master general of the IRA in favour of a peace strategy than for the UUP leaders to hold out against the young hardliners in the party.

But there are relatively few in any community who would dispute the award to John Hume: after all the years, the false alarms and, more recently, the hype and build-up to this year's award, when the news finally came that he had been chosen it almost seemed as if the whole of Northern Ireland emitted a collective "At last!"