Rishi Sunak is expected to travel to Northern Ireland later, after securing a deal with the EU that he promised would be a “turning point” for the region after years of post-Brexit tensions.
The new deal, dubbed the Windsor Framework, removes barriers on trade across the Irish Sea and hands a “veto” to politicians in Stormont on EU law – a set of concessions from Brussels that went further than some expected.
But it still includes a role for the European Court of Justice, with the Democratic Unionist Party and Tory backbenchers now set to study closely the details of the complex set of arrangements in the coming days.
The British prime minister, who is also expected to speak to backbench MPs on Tuesday, spoke at length in the House of Commons on the deal as he sought to see off any threat of rebellion from within his own ranks.
But the reception so far has been warm, with DUP leader Jeffrey Donaldson welcoming “significant progress” even as he warned that “there remain key issues of concern” regarding the deal.
The view of the party will be crucial, if the deal is to help restore powersharing at Stormont.
MPs are expected to get a vote on the deal, but Downing Street has not so far said when or how such a vote might take place.
A key part of the deal is an emergency “Stormont brake” on changes to EU goods rules that can be pulled by the Northern Ireland Assembly, with No 10 hopeful that it will ensure concerns over a “democratic deficit” are addressed.
The prime minister called it a “very powerful mechanism” for Stormont to use when it has concerns over EU law, as he heralded the overall deal as a “decisive breakthrough”.
“Together we have changed the original protocol and are today announcing the new Windsor Framework,” he said.
“Today’s agreement delivers smooth-flowing trade within the whole United Kingdom, protects Northern Ireland’s place in our union and safeguards sovereignty for the people of Northern Ireland.”
Leaders in the EU and beyond hailed the progress too, with Ms von der Leyen praising the “new chapter in our partnership” while French President Emmanuel Macron spoke of the “important decision”.
US President Joe Biden said it was an “essential step” in protecting the Good Friday Agreement, while in Dublin Taoiseach Leo Varadkar said that the EU had moved “a lot” to facilitate a deal.
Former prime minister Boris Johnson, who until only recently had been urging Mr Sunak to see the benefits of the newly-jettisoned Northern Ireland Protocol Bill, remained silent on Monday.
A source close to the former prime minister said that he is continuing to study and reflect on the government’s proposals.
But elsewhere within the Conservative ranks there was enthusiastic backing for the prime minister, with many senior Tories praising the deal.
Northern Ireland minister and former Brexit rebel Steve Baker was one of the most ardent backers of the prime minister’s deal, comparing the level of “statecraft” involved in the negotiations to that leading up to the Good Friday Agreement.
Speaking on ITV1’s Peston, Mr Baker said: “I think it’s a really historic moment.
“I think this is capable of bringing this awful rollercoaster row to an end, if the DUP are satisfied with it. I think it’s an incredibly important moment.”
Writing in the Telegraph, Chairman of the backbench 1922 Graham Brady said: “The so-called ‘Windsor Framework’ won’t be perfect but it looks like a massive step forward.”
Tory Brexiteers in the European Research Group (ERG) are to meet on Tuesday and will convene MP Sir Bill Cash’s so-called “star chamber” of lawyers to scrutinise the deal before deciding whether to back it.
The protocol was designed to prevent a hard border with Ireland after Brexit but means Northern Ireland has continued to follow EU rules on goods to prevent checks being needed when crossing into the Republic.
Unionists’ anger over the trade barriers in the Irish Sea culminated in the DUP collapsing powersharing in February last year, leaving Northern Ireland without an executive or an assembly.