It's fast becoming something of a cliche. But no less true for that. The Belfast Agreement, concluded on Good Friday, marked neither the end nor the beginning of the end - rather the end of the beginning.
Its achievement was truly remarkable. But now for the really hard part: making it work, and making it stick.
Against virtually all expectations, it became clear on Good Friday that David Trimble, the Ulster Unionist leader, had made the all-important leap of faith and imagination.
For two long years, the unionists had appeared to be engaged in little more than an exercise in blame allocation. Gerry Adams, the Sinn Fein president, frequently alleged that the unionist "engagement" was purely tactical and strategic. And there is little doubt that for many unionists the strategy was to avoid being blamed when the process, as they expected, finally fell apart.
However, the "inclusive" nature of the agreement tells us that, somewhere along that tactical road, David Trimble bought the idea that Gerry Adams and his colleagues might actually be serious about bringing the conflict to an end.
The terms of the agreement suggest he might also be right. The deal falls far short of declared republican goals. A united Ireland is for a future generation to decide. For the here-and-now, the North's constitutional position is settled; the principle of consent established; the Republic's territorial claim withdrawn.
These, taken together with the replacement of the Anglo-Irish Agreement and the establishment of the so-called "Council of the Isles", represent formidable unionist achievements.
But the unionist concessions are no less staggering: a partnership government to include Sinn Fein;
a North-South Council with the capacity for growth by agreement on both sides;
the phased release of prisoners over a two year period;
an independent commission to consider the future of the RUC;
a wide ranging equality agenda precluding any suggestion of "a return to Stormont".
The emerging `no' campaign confirms this is too much for many unionists to stomach. It is equally clear that many republicans think there has been inadequate reward for the long years of warfare and struggle. And bear in mind: Trimble and Adams managed to conclude the talks process without ever directly speaking to one another.
If the agreement is to hold, that - like everything else in Northern Ireland - will have to change and in double-quick order.
Assuming a `yes' vote on May 22nd (and that the anti-agreement unionists don't muster more than 60 per cent of the unionist seats in the assembly), all the proposed structures will come into being in shadow form in early July. David Trimble, as First Minister-in-waiting, will have to sit down at the cabinet table with the nominated Sinn Fein members of the new Northern Ireland Executive.
Just imagine that (leaving aside for the moment the drafting of the legislation for cross border bodies to come, or the vexed question of decommissioning and the consequences of a commitment by former paramilitaries to exclusively peaceful means) and you grasp the staggering ambition of this project.
The hope of both governments is that each side will find the pain of change evenly dispersed.
In the past, the North's politics have followed a simple rule of thumb: "If it's good for them, it's bad for us.' London's profound prayer now is that each side, knowing the consequence of failure, will resist the temptation to "cherry pick" the agreement - to claim the advantages and disavow the burdens and obligations the agreement would impose.
In short, Mr Blair's anxiety is that each side should claim "ownership" of the settlement and come to regard it as a significant advance on the status quo.
For a society so long driven by the imperatives of the `possessed' and the "dis-possessed", that is the greatest challenge. And, for a new generation, the challenge is to leave future history to those who alone can write it, to shape a present which refuses any longer to be bound by the past.
