The meeting in Berkshire, where King Charles II’s Windsor Castle is situated, suggests the UK and the European Union are finally ready to settle their differences over a stand-off that has persisted since the UK’s departure from the EU single market and customs union in 2021. Finalising Northern Ireland’s post-Brexit trading arrangements has been a hangover from the withdrawal agreement that the UK and the EU agreed in 2019, when Boris Johnson was Britain’s prime minister.

Announcing a deal would be a triumph for Sunak, who has sought to dial down tensions with the EU since taking power in October. But there could still be peril ahead for the premier, who was unable to convince unionists in Northern Ireland and Brexiteers in his own Conservative Party to endorse an agreement last week.

If a deal is reached, Sunak is expected to brief his Cabinet in the afternoon, alongside presentations from Foreign Secretary James Cleverly and the Secretary of State for Northern Ireland Chris Heaton-Harris, who have both been involved in talks. The premier will hold a news conference late afternoon before making a statement to Parliament. Both the Conservatives and main opposition Labour Party have instructed their MPs to attend Westminster. 

EU Brexit chief Maros Sefcovic will brief member states on Monday on the state of play, according to a person familiar with the plans.

When asked about reports that Von der Leyen, president of the European Commission, had been expected to travel to Britain on Saturday, and was to meet the king at Windsor Castle, Justice Secretary Dominic Raab downplayed the significance, telling Sky News on Sunday, “The king, the monarch, regularly meets heads of states and heads of leading international organisations.” 

The Mail on Sunday reported anger from Conservative MPs that Sunak was trying to involve the head of state in his Brexit plans. 

The deal would seek to soften trade and regulatory barriers that emerged within the UK as a result of the Northern Ireland Protocol – the portion of the Brexit deal negotiated by Johnson that governs the region’s unique place in both the UK and EU’s trading markets.

The proposed solution centres on “green” and “red” customs lanes for goods flowing from Great Britain to Northern Ireland and onwards to the EU respectively. That would end onerous checks and paperwork on goods travelling within the UK, Bloomberg previously reported. 

Sunak had been preparing to unveil a new deal last week, but vocal opposition from Northern Ireland’s Democratic Unionist Party and some pro-Brexit Tory MPs scuppered the plan. The DUP has refused to engage in the power-sharing administration at Stormont in protest at how the protocol creates a de facto border in the Irish Sea because goods being shipped from Great Britain to Northern Ireland must undergo checks. Sunak will be hoping his deal meets the DUP’s so-called seven tests to restore power-sharing in the province. 

Sunak told the Sunday Times he was “giving it everything” to try to strike a deal with the EU on the Northern Ireland protocol, saying he does not believe the deal would leave Northern Ireland in the “orbit” of Brussels. Even so, the deal is expected to reduce the influence of the European Court of Justice in Northern Ireland but keep it as the ultimate arbiter of disputes about EU law.

Mark Francois, leader of the European Research Group of pro-Brexit Tory MPs, said cutting the influence of the European court was not enough, telling Sky News on Sunday the DUP could not accept a Brexit deal where EU law was superior to UK law in Northern Ireland.

“Unless that legal text when we see it expunges EU law from Northern Ireland it’s very unlikely that the DUP will support it ,  less of a role is not enough,” Francois said. “We have to get rid of EU law in Northern Ireland.” He also warned Sunak not to try to “bludgeon” his deal through Parliament without a vote. 

A spokesman for the DUP declined to comment. BM/DM