The Northern Ireland peace process reached its improbable consummation yesterday, as Protestant fundamentalist Rev. Ian Paisley was sworn in as first minister of the province, with former IRA operative Martin McGuinness as his deputy.

Britain’s Northern Ireland secretary told the BBC that the two men “genuinely are getting on well”. The BBC’s correspondent added that they have an “easy chemistry”, and described them “work[ing] off each other like a well-established comedy double act.”

Even so, while the news reports show them standing side by side shaking hands with visiting dignitaries, no-one has caught them on camera shaking hands with each other.

It’s not unusual for extremists to have shared interests. Paisley and McGuinness have worked together, after a fashion, before: 35 years ago they were leaders of the most intransigent forces in their respective communities, both working to torpedo any attempt at a compromise settlement.

But anyone then who forecast that they would one day sit down amicably in government together would have been dismissed as a utopian. Only last year, Paisley vowed that it would happen “over our dead bodies”.

If there is a lesson from this saga, it’s that peace comes not from marginalising the extremists, but from painstakingly bringing them within the tent.

Back in the 1970s, the idea that the DUP and Sinn Fein would between them win a majority of the Northern Irish vote would have been cause for the deepest pessimism. But when that actually happened two months ago, it was a sign of progress. The electorate realised that for peace to work, the extremists had to be empowered: only they could make it stick.

And sure enough, when the old enemies finally sit down together, they find they have a lot in common.