One of the Tories’ tactical successes has been to push Brexit down the news agenda. But even if it

no longer dominates front pages and news bulletins as it once did, the task of sorting out Britain’s future relationship with the European Union remains the government’s biggest challenge. Brexit also providesthe best explanation for some of No. 10’s other actions.

Last week’s cabinet reshuffle, for instance, can only be properly understood in the context of Brexit. The purpose was to create an all-powerful centre. The three greatest parts of government — No. 10, the Treasury and the Cabinet Office — have now been joined together. There is a combined No. 10 / No. 11 economic unit and, just as significantly, Theodore Agnew is a Minister of State in both the Cabinet Office and the Treasury, which links those two motors of government together. Agnew is also a trusted ally of Dominic Cummings. Cummings, with Michael Gove, appointed Agnew to the board of the Department

of Education when Gove was Education Secretary.

The government is acutely aware that it has less than ten months to get ready for the end of the transition period. The hope is that this new structure will prevent anyone from attempting to delay or obstruct preparations for the end of December.

The Brexit celebrations on 31 January disguised the fact that, in practical terms, nothing changed the next day. Boris Johnson could throw a bash in No. 10, confident that goods were going to flow across the border the next morning. But when the transition period ends, the nature of this country’s borders will change in terms of both trade and immigration. On 31 December, no one in government will be throwing parties. Instead, they will be waiting anxiously to see what happens when the first lorries roll off the ferries at Calais and Dover.

Even if the government secures the Canada-style deal it wants, there will be — as the government acknowledges — friction at the border. How that friction is handled will be crucial to this administration’s prospects. If this country is unprepared and there is serious disruption, the government will be broken-backed. Like John Major after the UK was forced out of the exchange rate mechanism, Johnson would be in office but not in power. However, if the changes to the terms of trade are barely noticed by consumers, the Tories will remain favourites to win an unprecedented fifth term in the next election.

The EU believes that the British government’s vulnerability on this front is one of the EU’s strengths in the negotiation. In the event of a negotiated free trade agreement (FTA), the EU will take a cooperative approach to the border and take steps

to reduce the amount of friction; but if the talks collapse, then the EU will adopt a hard-line position. This will mean that it will require an even greater and more creative effort by the UK government to keep disruption to a minimum.

At the moment, the UK and EU sides are far apart on any future trade deal. However, both sides are more reconcilable than they appear at first blush. If they get their frustrations with each other out of the way early, there is still time for an agreement to be reached.

The second way in which the reshuffle was shaped by Brexit is that it was designed to ensure that the key government departments are all aligned on the subject. For the first time, every great office of state is now held by someone who campaigned

for Leave in 2016. Thanks to the reshuffle, this administration is united in the belief that the whole point of leaving the EU is to do things differently.

Before his resignation, Javid had accepted that there was going to be friction at the borders, and he told businesses to get ready for it. Behind the scenes, though, there

were big differences between the Javid and Johnson teams. Those close to Javid believed that more than a simple FTA would be needed to protect jobs in the manufacturing seats that the Tories won at the last election. This meant that they were more inclinedto make compromises to protect supply chains. By contrast, No. 10’s view is that decisions made in the UK will be more important to the economy of these places than border frictions.

By the end of this year, the UK and the EU must also agree on how to implement the Northern Ireland protocol. Johnson and the EU have very different views on what the protocol means in terms of checks on goods crossing from Great Britain to Northern Ireland. Two of the most important government figures in this respect were changed during the reshuffle. The Northern Ireland Secretary Julian Smith has been replaced by Brandon Lewis, and the Attorney General Geoffrey Cox by Suella Braverman.

It will be the Attorney General who advises the government on what its legal obligations are under the Northern Irish protocol. It seems reasonable to predict that No. 10 will find Braverman more congenial on this front than Cox. This Prime Minister was never going to be entirely comfortable with an AG who named his chambers after Thomas More.

The main reasons for Smith’s dismissal date back to September. No. 10 believed that his concerns about no deal meant he would be the next minister to walk out after Amber Rudd quit. But Smith’s attitude to the role, as shown in his diary on page 9, means that he would have resisted any attempt to reinterpret the protocol.

In 2019, the Tories rode to victory on the slogan ‘Get Brexit done’. But their fortunes at the next election will be determined by the impact of leaving the EU. The government has just 45 weeks to get the borders ready for the biggest changes seen in the post-war era.

If this new central method of governing can deliver that, then it will have justified its creation. If it fails, then it will be swept away as the old ways reassert themselves.

Every great office of state is now held by someone who campaigned for Leave