RISHI Sunak has signed a deal with the EU to replace the Northern Ireland Protocol - which could yet face challenges from Unionists in the province and hardline Brexiteers. 

The Prime Minister and EU chief Ursula von der Leyen finalised the much-delayed agreement to ease the trading issues created by the Protocol during a summit at Windsor on Monday, a senior Government source told the PA news agency.

“An agreement has been reached. The deal is done,” they said.

The European Commission president will go on to have tea with the King at Windsor Castle despite criticisms that the meeting would drag Charles into the politically contentious deal.

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Sunak hopes the deal will win the approval of the Democratic Unionist Party (DUP) so powersharing can be restored in Northern Ireland to get Stormont back up and running.

DUP support would also be key in convincing Conservative Brexiteers to back the deal as pressure mounted on the Prime Minister to give MPs a Commons vote.

Earlier in the day, Conservative Brexiteer Jacob Rees-Mogg warned Sunak of a possible Tory revolt if the DUP does not support the deal, despite major concessions expected from the EU.

The former cabinet minister told GB News: “It will all depend on the DUP. If the DUP are against it, I think there will be quite a significant number of Conservatives who are unhappy.”

He said that the position of Boris Johnson, who he described as the “biggest figure in UK politics”, will be “fundamental”.

But arch-Brexiteer Steve Baker, the Northern Ireland Office minister who had been on resignation watch, gave Sunak his support.

Leaving No 10, he told broadcasters: “I can only say this: that the Prime Minister is on the cusp of securing a really fantastic result for everyone involved.”

Charles’s meeting with von der Leyen was criticised as “constitutionally unwise” by Rees-Mogg because it involves the King “in a matter of immediate political controversy”.

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Baroness Arlene Foster, the former DUP leader and ex-first minister of Northern Ireland, said it was “crass and will go down very badly” with the unionists Mr Sunak is trying to win over.

Conservative Eurosceptic Theresa Villiers said it is “crucial” for Sunak to give MPs a vote on the deal, as Downing Street declined to commit to one.

The former Northern Ireland secretary told BBC Radio 4’s Today programme: “I can’t conceive of circumstances where something as significant as this could be finally agreed and implemented without MPs voting on it in parliament.”

She said she will consider the deal itself as well as talking to the DUP before deciding whether to support it, but stressed that restoring powersharing was “crucial”.

“It’s intolerable that we’ve got the protocol undermining political stability in Northern Ireland,” she said.

Keir Starmer reiterated Labour’s support for any deal but said the real test will be whether Sunak “has got the strength to sell it to his backbenchers or not”.

After a speech in the City of London, Starmer said it is “almost inevitable” that the European Court of Justice (ECJ) will “have to play some part” after the deal, a contentious point for the DUP.

But he said “we’ve got to make progress” on Northern Ireland before making “real changes” to the wider Brexit deal.

The Prime Minister will brief his senior ministers in a virtual meeting of the Cabinet.

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He will then rejoin von der Leyen to set out the deal to voters in a joint press conference before the Prime Minister makes a statement to MPs in the Commons.

Tory Brexiteers in the European Research Group (ERG) will convene MP Bill Cash’s so-called “star chamber” of lawyers to scrutinise the deal before deciding whether to back it.

The protocol, signed by Johnson as prime minister in 2020, was designed to prevent a hard border with Ireland after Brexit.

Northern Ireland has continued to follow EU rules on goods to prevent checks being needed when crossing into the Republic.

But the trade barriers created between Northern Ireland and Great Britain have angered unionists.

The DUP collapsed powersharing at Stormont last year in protest over the protocol, leaving Northern Ireland without an executive or an assembly.

Party leader Jeffrey Donaldson has issued seven tests that Sunak’s new pact will have to meet to win DUP backing.

Chief among them is addressing what he calls the “democratic deficit” of Northern Ireland being subject to EU rules while not having a say on them.

The deal is expected to include check-free lanes for goods coming from Great Britain into Northern Ireland.

Deputy Prime Minister Dominic Raab said the reduction in trade red tape would lead to a “substantial scaling back” of the role of the ECJ.

But he refused on Sunday to rule out the court having a say on future legal cases, which could prove to be a flashpoint for DUP resistance.

If Sunak does allow a Commons vote, he is likely to win because Labour has agreed to support it, but he would want to succeed without relying on opposition votes.