There are still obstacles to implementing the settlement provisionally endorsed by the UUP on Saturday. In particular, Gerry Adams, Martin McGuinness and their Sinn Fein colleagues have to secure the implementation by the IRA of the voluntary decommissioning to be initiated in January. This is despite the decision by David Trimble, under pressure from opponents, to introduce an unplanned deadline ultimately outside his control.

Given the skill with which these two and some of their allies have so far led their political movement, and persuaded the paramilitary wing to follow the path to peace, the odds must strongly favour such an outcome.

It would be absurd for Sinn Fein/IRA to abandon, at the very end, a strategy which has brought it to the brink of success just because of pique about the UUP Council retaining a decisive role until February.

Within the new executive, UUP members will have a strong incentive to work with their Sinn Fein colleagues during this trial period. The DUP decision to take its ministries but not to participate in meetings of the executive should facilitate this process. Not for the first time, Dr Paisley's negative tactics may prove self-defeating.

Happily, the lengthy talks have enabled the protagonists to establish an understanding of each other's problems and to develop trust and confidence in each other's good faith. This offers a firmer foundation for the construction of a viable polity and society in Northern Ireland than anyone could have expected.

This outcome could never have emerged if strong leadership had not been shown by many politicians in this State, Northern Ireland, Britain and the US.

Among these politicians we must now include Mr Adams, Mr McGuinness and those within Sinn Fein and the IRA who have supported their efforts.

Historians will tease out the threads of the process which has produced this outcome. In doing so, they will come to remark on several strange paradoxes.

First of all, by mishandling the hunger-strikes in 1980-81, the British government unwittingly increased tolerance of and support for the IRA in the North, and to a much lesser extent in this State. It was that unexpected rise in support which first drew Sinn Fein into parliamentary politics by causing it in 1981 to put forward H-Block candidates North and South. It later nominated candidates for elections in both parts of the island.

Once involved in politics, Sinn Fein wanted to preserve its new democratic base. This made it more responsive to the sensitivity of its electorate to violence.

The resultant conflict of interest between those who saw the way ahead as through violence and those newly engaged in politics created tensions which, over time, worked against its violent wing.

This offered the British government an opportunity to influence the outcome of the internal struggle within the republican movement by moderating security policies, improving conditions for the nationalist population and conceding to the Irish Government a role in relation to the interests of Northern nationalists.

Such measures would have had the capacity to swing nationalist votes away from Sinn Fein and back to the SDLP.

However, the British government, and in particular Margaret Thatcher, were very slow to recognise the potential value of this approach. Mrs Thatcher remained hung up on an exclusively security approach to the problem. This reflected a deeply-embedded, post-imperial attitude and was complicated by the difficulty which leaders of large countries often have empathising with smaller neighbours.

The problem was complicated by British defensiveness about its army, which had been engaged in policing duties in Northern Ireland since 1969. In practice, this gave the Ministry of Defence a totally disproportionate, and consistently negative, influence over the security policy pursued.

On the Irish side, the obverse of these phenomena has often been the kind of inferiority complex, and even paranoia, which smaller countries often feel towards larger neighbours. Such attitudes further complicated the Anglo-Irish relationship.

Fortunately, during the mid-1980s there were some ministers and civil servants free from such hang-ups on both sides of the Irish Sea. Intensive diplomacy by the government between 1983 and 1985 found some support within the British establishment.

So much so that the negotiation which ensued was not so much between Ireland and Britain as between Irish and British ministers and civil servants on the one hand and the British prime minister, Mrs Thatcher, on the other.

Eventually Mrs Thatcher was persuaded to sign an agreement directed towards weaning the nationalist community away from Sinn Fein. She did so with many qualms, for she had been intellectually, but not emotionally, convinced of its potential value.

As soon as it was signed, Mrs Thatcher reverted instinctively to the security-dominated mentality which had kept the conflict going.

Thus none of the four modifications of security policy provided for under the agreement - accompaniment of army patrols by the RUC, early promulgation of a police code of conduct, a change in the one-judge court system and early announcement of a modification of prison sentences in the light of a major reduction of violence - took place in the way or at the time agreed.

But - yet another paradox - happily for the agreement, Ian Paisley and Jim Molyneaux came promptly to the rescue. By organising massive opposition to the agreement, and by resigning their Westminster seats, unionist politicians convinced the nationalist population that the agreement must have been a victory for them.

Nationalists seem to have noticed neither the failure to deliver on the security provisions nor the substantial gains they secured on other fronts during 1986.

Unionist fury and dissatisfaction with an agreement, the purposes and significance of which they and their leaders totally failed to grasp, was loud enough to swing a third of Sinn Fein voters back to the SDLP.

This substantial post-agreement loss of support led the Sinn Fein leadership to rethink its "ballot box and Armalite" policy, leading it towards an abandonment of violence for a democratic approach.

Of course, the downside of the agreement was that, in the short run, it also made it less likely that unionists would be prepared to respond positively to such a change of stance by Sinn Fein.

BY the time Sinn Fein had completed its shift from violence to democracy and declared a cessation of violence - it took eight years - angry unionist memories of the 1985 agreement had dimmed.

A large section of unionism was preparing to contemplate the kind of Sunningdale-type solution which had formerly been rejected, even this time with a disarmed Sinn Fein/IRA in government as well as the SDLP.

The initial brunt of the task of preparing the way for such a development fell on John Hume. He had to persuade Sinn Fein to make the final move away from violence.

He also had to persuade the British government - now under the leadership of someone free from post-imperial hang-ups about Ireland, John Major - to seriously review its role in Northern Ireland. Mr Hume wanted Britain to formulate a positive attitude to the concept of Irish self-determination to be exercised separately, however, by the people of Northern Ireland.

On the Dublin side, successive Taoisigh carried this process through. Charles Haughey initiated the first indirect contacts with Sinn Fein as it approached the point of abandoning violence; Albert Reynolds secured the Downing Street Declaration; John Bruton negotiated the final version of the Framework Document; and Bertie Ahern played a crucial role in negotiating last year's Belfast Agreement and in overcoming obstacles to it.

On the London side, Mr Major and Sir Patrick Mayhew brought matters a certain distance. However, it was left to Tony Blair and Mo Mowlam to complete the laborious task of bringing the parties together and persuading unionists to negotiate, first indirectly, then directly, with Sinn Fein.

It has to be said that none of this would have got anywhere but for the determination and political skill of Mr Adams, Mr McGuinness and their Sinn Fein colleagues.

And there would never have been a Belfast Agreement, or a resolution of the decommissioning problem, if Mr Trimble, walking a perpetual tightrope and beset by enemies and often fearful friends, had not inched forward to what we must hope will be a successful outcome. This involves an executive permanently established and all the other complex institutional arrangements which have been agreed between the parties brought fully into operation.

The new settlement is a testimony to the capacity of late-20th-century Irish and British politicians of all parties. So much for cynics who so often deride politics and its participants.