Gerry Adams, Martin McGuinness and their associates went in by the front door, clutching nothing more lethal than briefcases and Filofaxes.
In receiving the Sinn Fein delegation Tony Blair must have believed he was talking to some of the leaders of the IRA, for he has said Sinn Fein and the IRA are inextricably linked. He held no illusions, in other words, about the hands he was shaking.
He was talking to them because he, like the Irish government and John Hume of the Social Democratic and Labour Party, subscribes to the concept of transition. He believes that even a movement with roots so deeply implanted in the use of force can be brought into politics. Some of this springs from new Labour pragmatism and impatience with the old stalemates, some from a cool judgement that the Adams leadership is serious about the unprecedented project of bringing the entire republican movement into politics.
At first this collided with the old Tory and Unionist belief that the Irish question was insoluble and that taking risks like this was futile since the republican leopard would never change its spots. Yesterday's encounter had its critics, of course, but it gave rise to little sense of a fierce outcry, outside media circles.
The peace process began life as an Irish nationalist creature, and was thus instinctively opposed by Unionists. But as the months have gone by buzzwords such as peace, talking and dialogue have taken root within the Unionist community too. First the businessmen, then some clerics, then even the paramilitary groups - some of whom have already been to Downing Street - slipped into peace process mode.
Now David Trimble, leader of the Ulster Unionists, regularly finds himself in the same room as Gerry Adams at the Stormont talks. And now Gerry Adams finds himself talking to Tony Blair in Number 10, facing the British prime minister and also facing some facts.
One key fact is that Irish unity is not to be found in the foreseeable future: any conceivable agreement will still leave Northern Ireland as part of the United Kingdom. Ergo, the sceptics say, the IRA will go back to violence.
Yet there is still much for republicans to gain from the process: a sense that they can make considerable interim advances, a sense that they may yet ultimately reach their goal, a sense of self-esteem.
Tony Blair will not have promised them the moon. He may well be content if he has bolstered their belief that politics can achieve more for them than that mortar attack ever did.Reuse content