By Mark Devenport
BBC Northern Ireland political editor
Anyone who has covered the Northern Ireland process has grown accustomed to "days like this".
There were helicopters overhead, the press camped out in tents on a lawn, VIPs talking about history to banks of cameras - but this day felt different.
Ian Paisley and Martin McGuinness pictured at Stormont
So often in the past, it has been incomplete or uncertain.
Carefully worked out sequences "put on hold" as one side feels let down by another.
People jumping first without knowing whether others will follow.
Dangerous opponents left on the outside, trying their hardest to bring the whole edifice down.
But not today. The diehard opponents of the process are now its lynchpins.
Politicians did not need to look before they leapt.
The careful choreography worked out precisely as intended.
The death of DUP assembly member George Dawson gave the start of the proceedings a sombre note.
But by the time the VIPs reached the Great Hall the mood was celebratory.
An aptly-named group, the Sky's The Limit, made up of young adults with special needs, provided the entertainment.
The newly elected first and deputy first ministers had different views on how we got here.
Ian Paisley claimed the day could have come sooner if outsiders had left well alone.
By contrast, Martin McGuinness thanked those from elsewhere who offered a helping hand.
There was no historic handshake.
But the first minister tapped the bannister on the stairs at the Great Hall in applause after the deputy first made his speech.
Tony Blair said he had lost count of the number of times people had told him that Ian Paisley wouldn't do a deal.
Funny that, I seem to remember he himself told me once that such a notion was "pie in the sky".
But as Ian Paisley himself put it: "That was yesterday. This is today. And tomorrow will be tomorrow."
Beset by election difficulties in Dublin, Bertie Ahern appeared grateful to get a chance to play the statesman.
Only 54, Tony Blair will soon walk out of the polished black door at Downing Street for the last time.
But at 81, Ian Paisley is for the first time in his life abandoning protest politics to take real power.
As they sipped tea, the first minister and prime minister joked about their differing career trajectories.
Tony Blair remarked that he might take a lesson from Ian Paisley and hang on until he's 80. Don't worry Gordon, he was only joking.
The DUP leader has provided the prime minister with as tasty a piece of "pie in the sky" as he could have imagined.
It might not banish the anguish of Iraq, but it's as meaningful a note as Northern Ireland could have provided for Mr Blair to go out on.
Martin McGuinness and Ian Paisley have taken power
Now it will be up to the local politicians to face up to each other over education, the health service and the economy.
They will wrangle about these issues, for sure.
But that is normal politics in a normal society: it is what Tony Blair called "a small ambition to anyone who has not lived through the abnormality of a society living on the edge".
Today Stormont is up and running. And for a change, it does not feel like politics here is clinging to the edge.