Yesterday morning, a Government source pointed to the fact that Mr Martin McGuinness would begin a series of political engagements in Washington DC at 5 p.m., Irish time, culminating in a 6.15 p.m. meeting with President Bush's point man on the North, Ambassador Richard Haas. "He'll want to have good news in his pocket as he goes in," the source predicted.
At 5 p.m. precisely, the IRA announced that decommissioning had begun. The timing represented further proof that the terrorist attacks on the US were the key to the republicans' change of strategy. Having been expected to hang tough on decommissioning until well into next year, the desire to remain onside with America appears to have forced movement.
But while the September 11th attacks were the battering ram that broke down resistance to decommissioning, the republican movement has also been feeling more pressure than ever from Dublin in recent months.
Early in the peace process, Sinn FΘin leaders' visits to Dublin involved handshakes with the Taoiseach on the steps of Government Buildings and tolerance of the internal republican difficulties on decommissioning.
But no more. A sharp chill was injected into the Government's relations with Sinn FΘin over the summer. This was partly due to Fianna Fβil concern over rising Sinn FΘin electoral power. The high profile Sinn FΘin got out of the successful anti-Nice campaign, together with intense and well-funded Sinn FΘin activity in key constituencies, alarmed Fianna Fβil. As this week's TG4 opinion poll from Kerry North has confirmed, it is almost exclusively Fianna Fβil seats that are under threat from Sinn FΘin.
But the more robust attitude to Sinn FΘin was not only down to narrow electoral considerations. The Government was deeply annoyed at the apparent last- minute failure in August to achieve an expected gesture on decommissioning.
"We felt the Weston Park talks in July produced a substantial package that should have brought the breakthrough but they didn't buy it," says a Government source.
The Government had high hopes in early August that the IRA announcement that it had agreed a method of putting arms beyond use with the de Chastelain commission would be followed by an act of decommissioning. But the act never came.
The grudging UUP response to the agreement with the decommissioning body contributed to the IRA's decision not to take the crucial further step. But Dublin made few allowances for this, making it clear the primary responsibility for breaking the logjam now rested with the IRA.
Dublin was also particularly annoyed that Sinn FΘin held out on policing, refusing to endorse the new arrangements supported by the SDLP, the Catholic Church and the Government.
But despite the new hostility from the Government, the republican movement showed no sign of concession on weapons.
With a late September deadline approaching, nobody expected any movement. The Irish and British governments appeared resigned to a lengthy suspension of the institutions. Some Irish sources speculated - without, it must be said, proffering any evidence - that republicans would wait until close to a general election in the Republic to make a move, thus boosting their profile as a party of peace shortly before polling day.
But then came September 11th. Sinn FΘin is right when it says the Irish and British governments used the attacks on the US to crank up the pressure on them.
In Irish and British statements, the renewed revulsion at terrorism after the suicide attacks on the US was linked with the detention of IRA suspects who allegedly spent time with FARC guerrillas in Colombia.
The Bush administration rowed in with the message that without movement on arms, Sinn FΘin would no longer find the warmth and tolerance it had found in the US in recent years.
And for Sinn FΘin, the welcome, the political support and the funding they find in the US is hugely important.
In Government circles over the past fortnight there has been a sense that this time it would happen. However, few would say it. They warned of previous false dawns, pointing especially to the disappointment of early August when movement was expected.
Now the Government will move to reinforce those in the republican movement who pushed for last night's historic development.
They will press for an early public statement of British intent to dismantle look-out towers and reduce the military presence, as agreed at Weston Park in July.
Government sources say they believe there will be some "leakage" of members from the IRA as a result of decommissioning.
But they say their information is that the leadership is in firm control and that the number walking out the door shouting "sell-out" will be small.
Most importantly, the Government is anxious to see the political institutions back in operation as soon as possible. UUP Ministers can be restored to office through a visit to the speaker of the Northern Ireland Assembly. More fraught is the need to have Mr David Trimble re-elected as First Minister before the November 3rd deadline.
The Government can only sit and watch the internal unionist process, hoping intense British pressure can ensure Mr Trimble receives enough unionist support to be re-elected.
If and when that happens, the most intensive working of the north-south institutions that the Government can manage can be expected in order to press home to nationalists - and in particular Republicans - that politics works.