Britain's exit from one of the world's biggest trading blocs concluded on December 31, 2020, just days after it clinched a narrow Brexit trade deal with the European Union, in its most momentous global shift since the loss of empire.
The deal, agreed more than four years after Britain voted by a slim margin to leave the bloc, put a stamp on a divorce that has shaken the 70-year project to forge European unity from the ruins of World War Two.
Under the "EU-UK Trade and Cooperation Agreement" Britain is no longer part of the European Union's single market and customs union, there are no tariffs or quotas on the movement of goods originating in either place between the United Kingdom and the EU.
Prime Minister Boris Johnson cast the deal as the final implementation of the will of the British people who voted 52-48% for Brexit in a 2016 referendum.
But a continued dispute between London and Brussels over the implementation of the 2020 Brexit treaty in the British province of Northern Ireland has put at risk the historic U.S.-brokered 1998 Irish peace agreement, known as the Good Friday accord, which effectively ended three decades of violence.
The protocol aims to keep the province, which borders EU member Ireland, in both the United Kingdom's customs territory and the EU's single market.