The big danger now is of a pincer movement on the new agreement, an unacknowledged alliance in which extreme republicans and extreme loyalists develop a deadly rapport aimed at bringing it down. One anti-agreement loyalist has already predicted "massive, massive violence," with what looked suspiciously like a gleam of anticipation in his eyes.
All the signs are that the big paramilitary battalions - the IRA, UVF and UDA - will not use violence against the agreement. None of them is going to love it, but none of them is going to rise against it. The probability is that Sinn Fein and the Ulster Unionists will eventually subscribe to it, though each will have their reservations.
But then there are the little groups who want nothing to do with all this talk about peace, and who contain disaffected IRA men or loyalists with enough guns and bombs and enough motivation to try and do something about it.
The INLA had what it will regard as the distinction of carrying out the last killing before agreement, shooting dead a Protestant man in front of his wife. Actions like these do not require a tremendous amount of work or brains or courage; but they can give rise to larger detonations of violence.
One of these republican outfits has already staged two mortar attacks and tried to get a large bomb over to England; another has wrecked a couple of town centres. They obviously pose great dangers, but there have recently been encouraging developments on the security front.
This group is largely based on the southern side of the border, where Gardai have been enjoying almost unprecedented success in finding bomb factories and intercepting bombs in transit. Since the renegade groups are so much smaller than the mainstream IRA, southern police must be able to devote many more resources to watching them.
North of the border the RUC is no doubt locked in an undercover war with the Loyalist Volunteer Force, whose primitive political thinking has evolved little further beyond the notion that, to quote them: "Any Catholic will do" (for their shooting attacks).
And politically there is the Rev Ian Paisley, publicly disavowing the LVF and its recent declaration of support for his line, but aiming to add David Trimble's to the collection of Unionist leaders' scalps which already adorn his belt.
It has to be remembered that a certain proportion of the Protestant population wants nothing to do with any agreement, for a variety of reasons. Some of them view majority rule as the only form of democracy; some of them see the history of the past decade as a stream of surrenders to IRA violence; some of them just hate Catholics too much to think of a deal.
Some of the above have until now supported David Trimble on the supposition that he was in the mould of hardline Unionist leaders who would never be prepared to give an inch. They, like everyone else, are now in the process of having to reassess him after watching him boldly opt for accommodation rather than confrontation.
Some of them will now turn for leadership to Paisley, who represents probably the greatest threat of all these disparate elements. One real problem is the approaching marching season, for a bad Drumcree in early July could provide him with a potent rallying-point.
The risk lies not in these elements singlely but in the danger that they might combine to create a whole which is greater than the sum of its parts, producing a chain reaction. A bomb here, a political reverse there, perhaps a provocative assassination; there are certainly realistic scenarios which could lead to dangerous crises. Ultimate success in this venture will take close monitoring and micro-management, not for weeks but for years.
Those are some of the difficulties. It is too early to say definitively, within days of such a huge development, what its chances of success are, yet its prospects do look good. The deal contains extraordinary material, and it was launched with the extraordinary sight of all those old enemies and opponents around that Stormont table, applauding together.
They weren't necessarily applauding each other, but they were giving their support to something to which all had contributed. It was a genuine new creation, something clearly more than the sum of its constituent parts, far-reaching as they are in themselves.
That feeling of common interest, rarely seen before now, will go a long way to sustaining the deal in some tense days ahead. It seemed, amazingly, to strike a balance of interest among those who still retain mutually exclusive aspirations.
Next Saturday will bring two key tests of how it is all going down among nationalists and among Protestants, for the Sinn Fein annual conference and a special meeting of the Ulster Unionist Council are to be held on the same day. We will learn then if these two poles of opinion have settled on a middle way.
But, to borrow a phrase from Mo Mowlam, just about everyone has come to accept that the status quo is not an option. The present limbo suits no one: this is no way to live, or to co-exist politically, or to raise the next generation.
Only a small percentage cling to the idea that they can achieve a Brit- free Ireland or a Catholic-free Ulster. Northern Ireland is to become what the demographics and the politics dictate that it must be: a British- Irish entity, 55 per cent Protestant and 45 per cent Catholic.
A new deal has been forged, and it is emerging from the strongest bedrock of all: the regretful abandonment of utopianism and the embracing of the new realism. It is tough for idealists to come down to earth but at the weekend some were already appreciating the enormous consolation which is on offer: the sense that after all the bloodshed and the discord a clean, fresh, new start is now up for grabs.Reuse content