After 40 years of violence and an utterly dispiriting sequence of derailed peace initiatives, the odds against a breakthrough in Ulster in a given week will always be slim. Expectations must nonetheless be managed, and Downing Street has been managing them hard of late. This was the Prime Minister’s task yesterday when asked about talks held in London between Hugh Orde, the Northern Ireland police chief, and Gerry Adams, the Sinn Fein president. Tony Blair affected an air of weary detachment and acknowledged that “all the possibilities are there” before insisting: “Whether it happens or not is not up to me.”

“It” would be an historic deal between Northern Ireland’s two largest political parties, encompassing the decommissioning of IRA weapons and the resumption of power sharing along lines set down six years ago in the Good Friday accords. Mr Blair’s weariness may be genuine; his apparent detachment is not, for the prize of such a deal, all bleak precedent apart, is perhaps closer than it has ever been.

For the first time since the elections last year that put the fate of the Province in the hands of the Rev Ian Paisley’s Democratic Unionist Party (DUP) and Sinn Fein, both groups appear willing in principle to make the concessions necessary for an over-arching agreement. At Mr Blair’s request, President Bush has intervened with phone calls to Mr Paisley and Mr Adams over the weekend, urging them to turn their hints into actual compromises.

If they do, there is hope that a deal would hold: it is the defining paradox of recent developments in Northern Ireland that republicans are likely to have more faith in an agreement with their hardline Unionist rivals than one reached with David Trimble’s moderate, and now weakened, Ulster Unionist Party. Meanwhile, at the governmental level, London and Dublin have expressed their willingness to consider a “peace dividend” of as much as £1 billion in public funds to go towards much-needed infrastructure projects that the DUP and Sinn Fein agree have been delayed by sectarian strife. They may have had a hand in the strife, but their agreement on anything is welcome.

Mr Paisley’s willingness to trust potentially unreliable partners is to be lauded. The effect has been instructive. He has conquered a lifetime’s aversion to talks with Dublin, and although the elimination of the IRA as a terrorist organisation remains his — and London’s — chief, non-negotiable goal, he has shown a willingness to contemplate its continued existence as “an old boys’ association”. Mr Adams’s meeting with Mr Orde likewise breaks new ground, but a firm and unambiguous commitment from Sinn Fein to full and transparent decommissioning by the IRA is now long overdue. To demand that weapons destruction be properly recorded, and not just witnessed, is entirely legitimate.

The looming pressures of next year’s election make this window of opportunity for Ulster a narrow one, but a similar chance may not present itself for years. It must be seized.