There was a significant shift in the mood music in Westminster this week.

The Prime Minister achieved a rare thing in politics: a breakthrough over the vexed question of the Northern Ireland Protocol.

While mainly of interest to those in Northern Ireland, this has far wider significance in both domestic and international politics. It could prove a key turning point in demonstrating that this Prime Minister can deliver on his priorities.

The Northern Ireland Protocol served its purpose at the time: it unlocked the stalemate which allowed then PM Boris Johnson to deliver Brexit, weeks after the 2019 General Election.

But it created a fissure within the internal market of the United Kingdom and friction with our trading partners in the EU and US.

Against most commentator's predictions, Rishi Sunak has skilfully resolved the Rubik’s cube of British politics. 

The complexity of allowing an open border for goods passing between two countries within the island of Ireland while maintaining an open border across the Irish Sea between Northern Ireland and Great Britain has defied and defined the relationship between the UK and the EU since the referendum in 2016.

While it remains early days to claim victory, with details of the deal still being carefully scrutinised, the omens look encouraging.

In Parliament this week both seasoned Conservative observers and Opposition party leaders were positive, so a vote looks likely to be overwhelmingly supported.

The position of the PM internationally has been significantly enhanced. It is clear he is trusted by the EU and the US. The imminent visit by President Macron at the end of next week may unlock progress on other intractable problems. This deal has been welcomed by President Biden, who may now engage in the 25th anniversary of the Good Friday Agreement this Easter, which could allow progress on other bilateral fronts with the US.

The deal makes imaginative use of existing procedures, such as a new Green Lane for goods removing routine customs bureaucracy. But crucially it also uses the existing consent mechanism within the Northern Ireland Assembly to apply a new 'Stormont brake' on new EU legislation impacting goods in Northern Ireland. This substantially resolves the democratic deficit over sovereignty, as the Assembly can reject imposition of new EU rules without recourse to the European Court. For this to be applied requires the Assembly to resume sitting, which may incentivise the DUP to come on board.

Rishi Sunak has delivered a deal with the EU, against the odds. If accepted in Parliament, this will give him political momentum, not just on this, but on wider issues. The pendulum in British politics may be starting to swing once more.