The flags outside embassies have been lowered, the countdown clocks have stopped. The United Kingdom is no longer a member of the European Union.

The country's 47 years of membership officially ceased at the stroke of 23:00 GMT (midnight Brussels time), more than three and half years after an in/out referendum exposed deep rifts across British society.

UK Prime Minister Boris Johnson marked the historic moment with his team at his Downing Street office, celebrating with English sparkling wine and an array of British culinary treats.

As the clock ticked down the final seconds, thousands of Brexiters celebrated outside Parliament and groups burned EU flags on the streets of London.

Anti-Brexit campaigners mounted several protests along the Irish border.

Under the terms of the withdrawal agreement between the UK and EU, Britain now enters a transition period until the end of 2020, meaning London will abide by most EU laws while their future relationship is hashed out.

Johnson must now achieve a trade deal with the EU - the world's largest trading bloc - within 11 months, a task most experts have described as ambitious at best, but his wider mission over the next five years will be to find a way to repair the country's divisions.

The years since the referendum have seen ugly scenes at protests and clashes between pro- and anti-Europe demonstrators, as well as bitter rhetoric dominating newspapers and appearing in Parliament, and fears of a return of Northern Irish paramilitary violence.

It's not over yet

But those who think Friday's official departure date marks an end to the chaos may yet be disappointed.

"We are not even at the halfway point in this process," said Scott Lucas, professor of international politics at the University of Birmingham.

"We are only going into the tough negotiations with the European Union - on the economic relationship; on the status of Northern Ireland; on the industry, agriculture, banking, and finance," he told Al Jazeera. "Even on basics such as will Britons have health insurance in Europe? What are the rights of EU citizens living here and of UK citizens living in Europe?"

Trade expert David Henig, the UK director of the European Centre for International Political Economy think-tank, agreed Johnson has a difficult task ahead of him.

Credit: Aljazeera