It took 11 gruelling months for negotiators from Britain and the European Union to hammer out the terms of a post-Brexit trade deal. But in many respects, the deal is already 4 1/2 years out of date.

The world has changed radically since June 2016, when a narrow majority of people in Britain voted to leave the European Union, tempted by an argument that the country would prosper by throwing off the bureaucratic shackles of Brussels.

In those days, the vision of an agile, independent Britain — free to develop profitable, next-generation industries like artificial intelligence and cut its own trade deals with the United States, China and others — was an alluring sales pitch. The buccaneers of Brexit promised to create a “Global Britain.”

That was before the anti-immigrant and anti-globalist-fuelled rise of President Donald Trump and other populist leaders who erected barriers to trade and immigration and countries turned inward. It was before the coronavirus pandemic exposed the vulnerabilities of far-flung supply chains, fuelling calls to bring strategic industries back home and throwing globalism into retreat.

In the anxious dawn of 2021, buccaneers are out of fashion. The world is now dominated by three gargantuan economic blocs — the United States, China and the European Union. Britain has finalised its divorce from one of them, leaving it isolated at a time when the path forward seems more perilous than it once did.

“The whole ‘Global Britain’ model doesn’t reflect the more protectionist, nationalistic world we’re living in,” said Thomas Wright, the director of the Centre on the United States and Europe at the Brookings Institution. “Becoming a global free trader in 2016 is a bit like turning into a communist in 1989. It’s bad timing.”

As Prime Minister Boris Johnson leads Britain into a post-Brexit future, he also risks being out of step politically.

The Brexit agreement with the European Union comes at the very moment that President-elect Joe Biden is replacing Trump’s “America First” credo with a message of mending alliances and collaborating to tackle issues like global health and climate change.

While the deal averts tariffs and quotas on goods crossing the English Channel, it is at heart about disentangling neighbours who had become deeply integrated over four decades. That estrangement, analysts say, is bound to weaken ties between the two sides in other areas, like security and diplomacy.

“Biden wants to see alliances and multilateralism and cooperation, and Brexit runs completely against that,” said Mujtaba Rahman, an analyst at the Eurasia Group, a political risk consultancy. “Brexit is graduating into a more difficult political context where it is running against the grain.”

Trump cheered Britain’s drive to sever itself from the European Union. As a reward, he promised to negotiate a trade agreement with Johnson, whom he cultivated personally. But Biden opposed Brexit and has ruled out negotiating new trade agreements until the United States improves its own competitive position. That nullifies one of the prime selling points of Brexit.