Does Rishi Sunak deserve his moment in the Northern Ireland sun?

Each time the deadlock in Northern Ireland seems impossible to break, and yet each time it has been broken, by heroic leadership, attention to detail and constructive ambiguity.

In 1998, Tony Blair secured a settlement that had eluded his predecessors since Lloyd George’s time. It held together for a while, until David Trimble’s Ulster Unionist Party was eclipsed by the nay-saying Democratic Unionist Party. In 2007, Blair did it again, bringing Ian Paisley Sr into Belfast’s government with Sinn Fein.

That deal held, more or less, until the strains put on it by Brexit – supported by the DUP but opposed by the majority of the people of Northern Ireland – broke it two years ago.

Now, the seemingly impossible has been achieved a third time. Each time is historic – and even if each time is less historic than the time before, Rishi Sunak is entitled to take credit for restoring the power-sharing government. This is not some mere administrative compromise, but the guarantee that Northern Ireland will continue to make progress away from the sectarianism and bloodshed of the past.

It required solving the insoluble, reconciling the irreconcilable and leading the unleadable.

As before, this breakthrough has a list of credits as long as any blockbuster. The name of Jeffrey Donaldson, the DUP leader, is high up on the bill. The internal politics of the DUP is hard for outsiders to understand, and it had seemed that most of the party would have been happy never to re-engage with the institutions of the deeply distrusted Good Friday/Belfast agreement.

Chris Heaton-Harris, the self-effacing Northern Ireland secretary, was recognised by Conservative Party members in the latest survey by the website ConservativeHome, rising from 22nd place to 4th in the cabinet beauty contest. Tory members must be the second-hardest crowd to please in British politics after DUP members.

Steve Baker, the former self-described “Brexit hard man”, played a role as a junior Northern Ireland minister. As did many civil servants who kept the show on the road. Michelle O’Neill, vice-president of Sinn Fein and the new first minister, has played a strong hand with a generosity of spirit that gave the DUP unpersuadables fewer excuses.

But Sunak is no grandstander flying into Belfast to try to run a victory lap on the shoulders of others. As Blair can attest, nothing gets done in Northern Irish negotiations unless the full beam of the lighthouse of prime ministerial attention is turned to them. This is Sunak’s achievement as much as earlier ones were Blair’s.

Like Blair, he needed two attempts. First, Sunak renegotiated the Northern Ireland protocol of Boris Johnson’s Brexit deal, replacing it with the Windsor Framework in February last year. This involved persuading the EU to re-open the UK’s withdrawal agreement, something it had insisted it would not do. The most satisfying part of that deal was putting it through the House of Commons, when Johnson, who had in effect admitted that his own deal was rubbish and that he had never intended to stick to it anyway, managed to muster only 22 Tory votes against it.

Then Sunak turned to the task of bringing the DUP on board. It looked as if he had alienated Donaldson by not involving the DUP in the Windsor Framework talks, but perhaps it was only possible to do the deal in two stages. And now Sunak has finally done the deal that Johnson at one point claimed to have secured: a trade border in the Irish Sea so frictionless it might as well not be there.

It is easy to mock the prime minister for swanning in to pose for photos with Northern Irish leaders and with Leo Varadkar, his Irish opposite number. But he has achieved something momentous that will allow him, if his time in No 10 ends up being a mere two years, to leave a positive legacy in the pages of history.