It was not, however, the inclusive occasion which the British and Irish governments had hoped for, since a Protestant boycott of the proceedings turned Stormont into a Unionist-free zone for the day.
But both governments have high hopes that David Trimble's Ulster Unionists and other loyalists will make their entry soon, possibly as early as today, thus bringing mainstream Unionists and the republican movement into the same process for the first time ever.
Former US senator George Mitchell called a plenary session of the talks to order at 2pm yesterday, with Sinn Fein and four other parties arrayed around the large conference table. The chairs set aside for five Unionist parties were empty.
At that moment Mr Trimble was eating soup and a roll in a Belfast city centre cafe, affecting not to notice the five television camera-crews capturing his every movement. The exercise seemed to be a studied show of nonchalance in the face of mounting pressure to go to the talks, and a determination not to be dragooned to the table prematurely.
Instead of attending at Stormont he made arrangements to meet Mr Mitchell later in a nearby hotel, rather than going to Stormont, for discussions on what he described as "the precise procedural arrangements for our involvement".
The two governments have floated the idea of a procedural motion which would allow the talks to make a start on substantive issues even in the absence of the Unionists. But, since a statement from Mr Trimble said that if his party's concerns are met "we intend to be present at Castle Grounds as soon as possible", his appearance as early as this morning is regarded as a possibility.
There is speculation that the use of the phrase "Castle Grounds" rather than "Castle Buildings", where the talks are being held, could mean the Unionist party might decide to go to Stormont while refusing to enter the same building as the republican delegation.
Mr Trimble's conspicuous refusal to be rushed meant that, for once, at least some of the media focus was distracted away from Sinn Fein, though at Stormont itself the main event of the day was the arrival of party president Gerry Adams and his talks team.
He said: "We do think this could be the beginning of the end of conflict on this island." Of the Unionists he said: "If they are not here today they will be here tomorrow, or the day after or the day after - and the sooner the better for everyone."
This was just one item on a hectic political schedule aimed primarily at easing the Unionists' path to the table. The chief element was a joint statement from Prime Minister Tony Blair and the Taoiseach, Bertie Ahern. This both emphasised the principle of consent and affirmed that the two governments saw the resolution of the arms decommissioning issue as an indispensable part of the process of negotiation.
Although the Unionist party would have much preferred the word "mandatory" to "indispensable", it regarded the statement as representing a useful advance on the governments' positions.
Later, Paul Murphy, minister for political development, went to Unionist party headquarters for talks with Mr Trimble and others.
From parties within the talks came criticism of the Unionists, the Social Democratic and Labour Party speaking dismissively of "contrived drama". Monica McWilliams of the Women's Coalition said: "It is boys playing war and I am angry about it. We have one more year to put this thing right and the time is now and today."
Mark Durkan of the SDLP said: "We don't want to make things difficult for David Trimble. If there are things needed to give him and the Ulster Unionists a few more cushions to make them comfortable sitting with Sinn Fein, okay. If however they're looking to change the furniture and the architecture of the place then that's a different matter."
A poignant note was struck by the appearance outside the talks of Rita Restorick, the mother of the last British soldier to be killed by the IRA. Holding a photograph of her 23-year-old son, Stephen, she said: "I want all the parties to take part and try and find a resolution, but both sides will have to make compromises. I felt I had to come for the benefit of the ordinary people and although I'm not overly optimistic, I want these talks to succeed."