LONDON – Inflammatory warnings from politicians. Knife-edge votes in Parliament. A looming election against a backdrop of national crisis. Britain’s ruling Conservative Party has been caught up in a clamorous debate over deporting asylum seekers to Rwanda, which has at times sounded like a not-so-distant echo of Brexit.

Yet for all the fury it has generated, the Rwanda plan is little more than a sideshow in the surprising story of immigration in post-Brexit Britain. While refugees who make hazardous crossings of the English Channel in rickety boats pose a humanitarian challenge, they constitute a fraction – less than 5 per cent – of the number of people who immigrate to the country legally every year.

Far from closing its borders, Britain has thrown them open since voting in 2016 to leave the European Union. And as the coronavirus pandemic has subsided, legal immigration has exploded. Net legal migration – the number of people who arrived minus those who left – reached nearly 750,000 people in 2022. That is more than double the number in the year before the Brexit referendum.

Immigration is replenishing Britain’s labour force and deepening the diversity of its cities – a deliberate, if largely unspoken, strategy that has come as a rude shock to people who voted for Brexit on the promise that it would make the country’s borders less porous. And that has made it a volatile political issue for the Conservative Party, which played on fears of a foreign influx to propel the Brexit campaign, only to find itself presiding over a new era of mass legal migration.

“The Brexit Betrayal Is Now Complete,” said a headline in The Daily Telegraph, a normally pro-Tory newspaper, after the latest figures were released.

Ms Madeleine Sumption, director of the Migration Observatory at Oxford University, said “there is a sort of left-hand, right-hand issue” with immigration.

The government’s blustery messaging – Prime Minister Rishi Sunak recently warned that migrants could “overwhelm” the country – is often belied by its actions, she said, most visibly in Brexit’s core trade-off: While Britain cut back immigration for EU citizens, it loosened restrictions for people coming from many other parts of the world.

There were also important one-time boosts to the numbers. Britain has taken in some 174,000 refugees from Ukraine and about 125,000 British overseas passport holders from Hong Kong, who were granted residency after China imposed the national security law on the former British colony.

But even discounting those effects and other recent policy changes that are expected to lower legal immigration numbers over time, Britain has become an indisputably more ethnically and racially diverse country than it was before Brexit.

What has changed is the kinds of migrants who are granted visas. There are fewer young people from Italy and Spain working as waiters in London restaurants, and more medical professionals from India and the Philippines working as doctors and nurses in Britain’s understaffed National Health Service (NHS). There are fewer Polish plumbers, and more Nigerian graduate students.

That shift is by design: Brexiteers promised that if Britain were unshackled from the EU, it could devise a policy that would attract the best and the brightest from around the world.

When the post-Brexit immigration system came into force in January 2021, the previous cap on visas for skilled workers was scrapped, as was a requirement that employers show jobs could not be done by British residents.

Predictably, arrivals spiked. In 2013, 33,000 people emigrated to Britain from India. A decade later, it was nearly eight times that number, at 253,000.

So important is this new wave of migrants to Britain’s economy that some experts argue that immigration policy should be viewed as an unexpected dividend of Brexit. The new arrivals are keeping hospitals and nursing homes running and paying the upkeep at tuition-starved British universities.

“To give at least one section of the Brexiteers credit, their commitment was to have a system that was non-discriminatory, based on skills and salaries,” said Professor Jonathan Portes, who teaches economics and public policy at King’s College London. “It is a lot closer to delivering on the promise of Brexit than anything else they’ve done.”

And yet it is a success that is almost taboo for Mr Sunak. He was an early supporter of Brexit, which was sold as a lever to regain control of Britain’s borders. To the extent that he talks about immigration, he has vowed repeatedly to “stop the boats” crossing the channel – so far, having failed to do so.

“If we do not tackle this problem, the numbers will only grow,” he declared at a recent conference in Rome organised by the hard-right party of Italy’s Prime Minister Giorgia Meloni. “It will overwhelm our countries and our capacity to help those who actually need our help the most.”

The Migration Advisory Committee, an independent panel which advises the government, said there were reasons to expect a “significant decline” in the numbers in the next few years. But it said immigration would not dip to very low numbers without other major policy changes.

British doctors and nurses, for example, are fleeing the NHS, which is struggling to recruit home-grown replacements because of low wages and gruelling work conditions. The committee called for better wages, saying that “we remain deeply disappointed that the British government continues to exhibit no ambition in this area”.

Mr Sunak has not set a target for net migration, which experts said was wise because previous Conservative prime minister David Cameron was haunted by his pledge to cut new arrivals to the “tens of thousands”.

It is not clear what the optimum level of legal immigration should be. That is a complex political and economic calculation that involves long-term demographic trends, questions about population density and issues of social cohesion. It is vexing Western countries including France, which just passed a strict new immigration law, and the United States, where the southern border looms large in the 2024 presidential race.

In Britain, images of refugees landing on beaches in unseaworthy boats are posted on social media by Mr Nigel Farage, a populist politician and broadcaster who turned immigration into an emotive issue before the Brexit vote. His new party Reform UK, a descendant of the Brexit Party, threatens to siphon votes from the Tories.

One of the riddles of the current immigration debate, however, is why the broader population remains relatively relaxed about the record numbers, when people were far more hostile a decade ago. It may reflect a recognition that Britain is suffering a labour shortage, which would be even more acute without the new arrivals.

Another explanation, experts said, is that the migrants are gravitating to larger cities, where the hospitals and universities are. These destinations are already more diverse than towns and villages, where the influx of outsiders a decade ago was more noticeable – for example, fruit and vegetable pickers from Eastern Europe.

“People notice it in emergency rooms, but they don’t mind that because they know the NHS is in crisis,” said professor of politics Rob Ford at the University of Manchester. “When you see highly skilled professionals who are non-white, it’s very different when you had unskilled migrants from Poland or Romania, moving into rural areas, speaking no English.” NYTIMES