Lord Frost’s resignation is bad news for Boris Johnson, though that’s a side matter. Prime ministers come and go, what matters is policy. Lord Frost represented the most assertive face of the government on Northern Ireland and whether the UK or the EU ultimately decides that country’s fate. No one who replaces him is going to be as committed to his position on British sovereignty. No one who replaces him will be as prepared to have unpleasant meetings with Brussels (and Dublin). Be they major or minor, spectacular or subtle, concessions are coming.

One of the flaws in the ‘Get Brexit Done’ slogan — the slogan upon which Johnson won an 80-seat majority — is that Brexit is a process rather than an event. It wasn’t enough to win the referendum, Brexiteers then had to fight and ultimately throw out a parliament that refused to implement the result of the 2016 vote. With Britain formally out of the bloc, the task was winning the peace — making sure that Brexit proceeds on the most favourable terms possible to the UK.

The Northern Ireland Protocol is not favourable to the UK and was agreed to for reasons of political expediency. The EU had the UK in a corner and played its hand formidably. It was — or should have been — evident from the outset that the Protocol could not survive in its current form in the long term. Even with regard to Northern Ireland’s particular constitutional status, the NIP is a concession of sovereignty that most other governments would not make or be allowed to make. That this government did speaks ill of the importance attached to Northern Ireland’s place in the UK by political elites, policymakers and, glumly, the British public.

Lord Frost’s willingness to talk plainly and carry the big stick of invoking Article 16 would have been unimaginable had a civil servant been given the role. (If a civil servant was put in charge of our negotiations with Europe, we’d have been back in the EU within 12 hours and joined up to the euro in 24.) He ruffled feathers because what he stood for — an assertive UK unashamedly pursuing its interests — was so novel and especially so in relation to Northern Ireland.

Brexiteers were sold Boris as their man in government, and though many may wish to pretend they never bought it, most slammed their money down and didn’t so much as wait for a receipt. In fact, Lord Frost was their man, or at least the man of those who see the UK as more than just England. His departure is not merely a political problem for the Prime Minister. It removes from government a mindset and an approach to policy that, even if they don’t realise it now, Brexiteers will sorely come to miss.