By Staff, Agencies

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 neighbors.

The United Kingdom’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 that still remain raw.

Legally, Britain left on January 31 but has been in a standstill transition period during fractious talks to a 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 27 EU states.

Meanwhile, 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.