LONDON, UK (AFP) — Brexit becomes a reality on Thursday as Britain leaves Europe’s customs union and single market, ending nearly half a century of often turbulent ties with its closest neighbours.

The UK’s tortuous departure from the European Union takes full effect when Big Ben strikes 11:00 pm (2300 GMT) in central London, just as most of the European mainland ushers in 2021 at midnight.

Brexit has dominated British politics since the country’s narrow vote to leave the bloc in June 2016, opening deep political and social wounds which remain raw.

Prime Minister Boris Johnson, a key Brexit architect, said Thursday that Britain’s destiny “now resides firmly in our hands,” shortly after MPs approved his trade deal with the EU.

Legally, Britain left on January 31 but has been in a standstill transition period during fractious talks to secure a free-trade agreement with Brussels, which was finally clinched on Christmas Eve.

Once the transition ends, EU rules will no longer apply, with the immediate consequence being an end to the free movement of more than 500 million people between Britain and the 27 EU states.

Customs border checks will be back for the first time in decades, and despite the free-trade deal, queues and disruption from additional paperwork are expected.

Johnson told Britons that “the destiny of this great country now resides firmly in our hands,” in a statement released by his Downing Street office.

“This moment is finally upon us and now is the time to seize it,” he said.