BRUSSELS — His 13th-floor office with its panoramic views was testament to the high status Claude Moraes had attained as a senior member of the European Parliament. But on a recent morning, it was empty, save his suitcase, a laptop and phone on his bare desk.
That is because Mr. Moraes is British, and his time in Brussels is up.
For Britons back home, the formal departure from the European Union on Friday means very little in practice, as the country will obey European Union rules until the end of the year.
But it is different in Brussels. The longstanding British contingent in the European capital now has to disband, or regroup. Thousands of British permanent officials, lobbyists and others are actually staying in Brussels, and many have qualified for passports from Belgium — a nation that the British have more often mocked than admired.
But for Mr. Moraes and many others, it has meant joining the “Brexodus” of those quitting Brussels and their country’s 47-year engagement with its Continental neighbors, a cause to which many have devoted their careers.
Mr. Moraes had no real choice, because Britain is withdrawing its elected politicians from the European Parliament, where he spent two decades. But after the perpetual, nagging uncertainty of three missed Brexit deadlines, at least this is a moment of clarity.
“It was death row, but it was death row with a timetable,” said Mr. Moraes, who had little to pack because he never invested emotionally in the prime office that he won last summer and knew he would probably have to surrender. “I felt a little like an immigrant — a little like my childhood.”
Mr. Moraes knows how it feels to leave a country quickly: He moved to Scotland as a youngster after his family was deported to India from Yemen. He says his future is unclear, although he is close to accepting a new job in Britain.
For Britons working in Brussels, the 2016 referendum on European Union membership produced feelings akin to “grief or bereavement,” Mr. Moraes said. After that, each new deadline induced a wave of anxiety because, until last month’s general election, there was no certainty when — or even if — Brexit would happen.
“It was a real psychological drama, and it was a drama that was disconnected from your own country,” he said. “Nobody knew much about it back home, and nobody wanted to know much about it back home.”
A member of the European Parliament since 1999, Mr. Moraes has served as the chairman of the Civil Liberties, Justice and Home Affairs Committee and was most recently vice president of the Parliament’s center-left grouping.
At farewell events in the European Parliament this week, no one knew quite what note to strike, as lawmakers handed back their voting cards and office keys. In his office, Chris Davies, a Liberal Democrat lawmaker, showed a gracious written tribute from a political opponent. He said he knew that it was well intended, but that it nevertheless was a bit like reading his own obituary.
The past year has been bittersweet for Mr. Davies, who said he had “returned from the dead” politically. Having lost his European Parliament seat in 2014 after 15 years in office, he was elected again last year and made chairman of the Fisheries Committee.
His final visit to the Parliament’s other home, in Strasbourg, France, was an emotional one.
“I did cry going into the chamber — eyes very moist. I thought, ‘This is the last time I shall go in here,’” he said, adding that Friday would be “the end of me and my political career.”
“I love this Parliament, and I love the fact that you are working with people from 27 other countries,” Mr. Davies said.
The experience was markedly different from his time as an opposition lawmaker in the British Parliament in the 1990s.
“I was in the House of Commons for 20 months. I spoke 30 times, I introduced four parliamentary bills and asked hundreds of questions — achieved nothing,” he said. “Coming back here, you felt relevant again, like a grown-up job.”
Not everyone was shedding tears.
Rupert Lowe, a European lawmaker for the Brexit Party who campaigned for Britain to leave the bloc, said he saw the European Union as nothing more than a protectionist racket designed to destroy the nation state. “I am delighted we are leaving the European Union to take up our rightful place in Europe,” he said.
But even Mr. Lowe, who was elected last summer, became a little misty eyed when reflecting on his Continental adventure. “I’ve loved it,” he said. “It is a great place to come, a bit like being back at school.”
“If somebody was happy to pay me for staying here,” he added, “I would stay.”
For those who have made a career in European Union institutions or in related jobs like consultancy and lobbying — and who are therefore paid to stay in Brussels — the obvious course is to secure another nationality. Citizens of member states are allowed to live and work anywhere in the bloc, but Britain’s withdrawal complicates things for Britons who hold no other citizenship.
European officials are generally well paid, and most of those working in European Union institutions have been told they will not lose their jobs. But their prospects of promotion are no longer so secure. Support from national governments is normally needed for top posts, and some officials say that Britons are already being pushed into less important work.
The numbers are hazy, but of more than 1,000 Britons who are permanent officials in Brussels, about half are thought to have gained another passport.
Those with a grandparent born in Ireland can generally apply for an Irish passport, and people can be eligible for Belgian citizenship after five uninterrupted years of residence in the country. But language requirements and other complications can leave some applicants battling unsuccessfully for years.
Some who admit to having mocked Belgium in the past (a standard British insult is to ask someone to name three famous Belgians) are now defending the country in online debates.
“In the European institutions, there was a stampede for alternative passports,” said Peter Guilford, a trade consultant and former European Commission official. “A lot of people managed to flip their passports, mainly to Irish or Belgian.”
But a new passport does not necessarily solve the problem. “If you are British but have an Irish or German passport, everybody knows it and you are not considered a ‘real German’ and won’t get given the serious policy job,” he said. “You have a career, but you are not going to get the top jobs.”
Nonetheless, Mr. Guilford said that when he wrote on Facebook that he had received his Belgian passport, he was “deluged” with people wanting to know how to do it.
“It has made me appreciate Belgium more,” he added. “I have had some people saying I have betrayed my country and all that sort of stuff, which I consider to be just not serious. I haven’t stopped being British.”
Jacki Davis, another new Belgian from Britain, said there was “a lot about Belgium I don’t understand, but there is a lot about the U.K. I don’t understand.”
Ms. Davis, a former journalist who is now a senior adviser at the European Policy Center, a research institute, confessed to a moment of cultural confusion when she realized that she did not know Belgium’s national anthem. (She is not alone: A Belgian politician once mistakenly sang the French anthem instead.)
“I thought that when I found it and played it, I would immediately recognize it,” she said, “but I swear I have never heard of it in 30 years in the country.”