The UK and European Union (EU) have reached agreement on changes to the Northern Ireland Protocol.
"An agreement has been reached. The deal is done," an anonymous British government source told media on Monday afternoon.
British prime Minister Rishi Sunak and Ursula von der Leyen, president of the EU's executive the European Commission, met for talks in Windsor, just west of London, at lunchtime.
Von der Leyen was also reportedly granted an audience with King Charles III at Windsor Castle.
At a press conference later in the afternoon, Sunak said they had re-written the agreement, which he re-dubbed the "Windsor Framework," in three key spheres.
Sunak said the deal "delivers the smooth flow of trade" with a "green lane" for goods destined to be sold in Northern Ireland, with far less red tape — and no need to complete customs forms for online purchases from the mainland.
"We have protected Northern Ireland's place in the UK," the PM added, including VAT and excise changes such as cuts to alcohol tax.
The new agreement also allows the UK to veto the application of changes in EU legislation in Northern Ireland — if the devolved Stormont assembly votes to "pull the brake."
Von der Leyen said she and "dear Rishi" had agreed the "Windsor Framework," but only "in principle" — suggesting that it would have to be ratified by leaders of EU states as well as by Westminster.
She insisted that the revised agreement would preserve the 1999 Good Friday Agreement, which ended three decades of sectarian terrorism in Northern Ireland. And she condemned the shooting of Police Service for Norther Ireland (PSNI) Detective Chief Inspector John Caldwell in Omagh last week.
Sunak said MPs would get a vote on the deal at an "appropriate time," and that their opinion would be "respected". He and other government ministers have been evasive on whether Parliament would have the final say on any compromise with Brussels.
Minutes before the news of a deal broke, Northern Irish Democratic Unionist Party (DUP) leader Sir Jeffrey Donaldson said he was ambivalent about the prospect of a deal.
"I'm neither positive nor negative," Donaldson said. "We need to take time to look at the deal, what's available, and how does that match our seven tests."
The protocol, an annexe to the UK's 2020 post-Brexit withdrawal agreement with Brussels, keeps the UK's exclave of Northern Ireland within the EU's single market.
The Republic of Ireland, a member of the bloc, insisted that 'backstop' arrangement was necessary to avoid a 'hard border' with customs checks that might breach the terms of the Good Friday Agreement.
But that has meant customs checks on goods coming from mainland Britain and even bans on certain products like sausages and potted nursery plants. That has angered the majority unionist community, leading to unrest and a hoax bomb threat to Irish Foreign Minister Simon Coveney.