LONDON  — Britain officially leaves the European Union on Friday after a debilitating political period that has bitterly divided the nation since the 2016 Brexit referendum.

Difficult negotiations setting out the new relationship between Britain and its European neighbors will continue throughout 2020.

This series of stories chronicles Britain’s tortured relationship with Europe from the post-World War II years to the present.

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If Britain’s Brexit referendum revealed a nation divided, the ensuing three and a half years of figuring out how the country should actually leave the European Union have showcased all the fissures running through the fabric of British society.

Chasms between young and old, city and country, rich and poor. Take your pick.

The time since the Brexit vote in June 2016 has involved unprecedented levels Parliamentary rancor, public anger and distrust th at raise real questions about the ability of anyone to bring the country together again anytime soon.

Irreconcilable differences of opinion, and not just on Brexit, can be just that — irreconcilable.

The British Parliament was the main venue where much of this Brexit psychodrama played out. No gathering of lawmakers or TV broadcasters would be complete without protests by the “Stop Brexit Man,” also known as Steve Bray, and his simple and booming message relayed through a foghorn.

The Brexit process, with hindsight, could have played out in any number of ways. It could have been more consensual but that opportunity wasn’t long for the taking.

Prime Minister Theresa May, who succeeded David Cameron after he announced his upcoming resignation on the steps of 10 Downing Street on June 24, 2016, must take her share of the blame for the chaos that ensued.

May, who in the referendum backed the side that wanted to remain in the EU, took office just weeks after the Brexit vote and crucially before the full implications of leaving the EU had been fully digested — or planned for.

“Brexit means Brexit,” she said, a mantra that left many scratching their heads.

She formally set the process in motion by triggering Article 50 of the EU treaty on March 29, 2017, which gave Britain two years to negotiate an EU withdrawal deal. But in a serious miscalculation, she called a general election in June that year, hoping to boost her mandate. The vote cost her Conservative party its majority in Parliament, leaving May — and her Brexit plans — in an awkward limbo.

Without a majority of lawmakers to support her, May’s plans got blown this way and that by rival Brexit factions within her party. O pposition parties, meanwhile, launched a burgeoning effort to build a consensus behind holding another Brexit referendum. The EU repeatedly sought clarity from May, but was more often th an not left befuddled.

Eventually, May reached an agreement with EU leaders in the fall of 2018, but it failed to get support in Parliament. The first time she presented the bill for a vote, she endured the biggest-ever defeat for a sitting government.

It wasn’t much better the second time round. May’s Brexit bill was defeated again a third time, though by a much smaller amount, as many pro-Brexit Conservative lawmakers started fretting about the possibility that Britain may actually not leave the EU.

May then sought to build cross-party support — but many would say that was three years too late — and that effort failed too. After getting an extension to move Britain’s scheduled departure date from March to Oct. 31, 2019, she tearfully announced that she would be standing dow n in July.

That left her among the ranks of Conservative prime ministers whose time in office has been overwhelmed — and cut short — by the issue of Europe.