Three hours before Brexit, Eurostar 9061 pulled out of Gare du Nord, pushing steadily through the grimy suburbs of northern Paris, picking up speed across the flat plains of Picardy, through the Channel tunnel and onwards to St Pancras.

The 8.13pm service was the last train on the last day of Britain’s 47-year membership of the European Union. For many on board, it was also the last European journey they would be making as an EU citizens. For most, it was a bit of a moment.

Some had actively made it so. “We decided to mark this day because … we could,” said Nik Brown, 27, a Southampton vet, who with his friends Hannah de Spon, 34, and Mairead Ralph, 35, had caught the early train out to spend 11 hours in Paris.

Facebook Twitter Pinterest Nik Brown, Mairead Ralph and Hannah de Spon had spent the day sightseeing in Paris. Photograph: Martin Godwin/The Guardian

“We saw the Eiffel Tower and the Arc de Triomphe,” said De Spon, an animator. “We went to animé shops; that’s our thing. We had a cafe lunch. Everyone was so friendly, like they wanted to make our day. It just feels like we’re kicking them in the teeth.”

Brexit was “so silly, and wasteful”, said Brown, his UK passport stashed in an ‘I voted remain’ cover. “It seems so obvious we’re better as a community; coming together, not pushing apart. So anyway, we decided, at Christmas, to have today in Paris – our last day as Europeans.”

Others had only just clicked. “It realised as I was boarding,” said James O’Leary, 26, a software sales executive who travels to Paris once a week. “It was, yes, a moment. Rather a melancholy one. I think maybe none of us yet appreciates quite how much of a deal this is. Maybe we won’t fully understand what we’re missing until it’s gone.”

Facebook Twitter Pinterest James O’Leary travels to the French capital once a week. Photograph: Martin Godwin/The Guardian

Concretely, of course, very little will change for these travellers before the transition period ends next January. The 11 million passengers who take a Eurostar train each year will still have to show their passports, twice – Britain has never joined the passport-free Schengen zone.

But today was nonetheless a moment, agreed Pirashani Umassudan, 22, a student returning from a three-day break in the French capital. “It just means I’m losing a part of my identity,” she said. “A part that’s to do with acceptance, inclusion, union, friends. It’s not a good feeling.”

Callum McRobbie, 29, and Verity McQueenie, 26, from Northamptonshire, were on their way back from Disneyland Paris and wondering whether the next time they made the trip they might need to queue in the non-EU passports lane, with a visa.

“It feels quite surreal,” said McRobbie, a painter and decorator. “People are really devastated.” Brexit was doing damage all around, he said: a close Polish friend had gone home because of the uncertainty; he was not sure when, or if, he would return.

Facebook Twitter Pinterest Callum McRobbie and Verity McQueenie were returning from Disneyland Paris. Photograph: Martin Godwin/The Guardian

McQueenie, a deputy sister in an A&E ward, said her hospital was “really struggling. We’re losing people, lots of Europeans, and having trouble recruiting new ones.” The whole project, in fact, felt wrong, McRobbie said.

“I don’t like divides,” he said. “It just feels … like we’re putting up barriers, a fence is going up between us.” Nearly 50 years his senior, John Earwicker, a retired charity worker from Abingdon returning from a city break in Paris, felt the same.

“I feel it most keenly for my grandchildren,” he said. “The freedom we’ve had, to travel, work, live on a continent to which we are so closely tied by our culture and our heritage … They won’t have. And on the basis of such empty, meaningless slogans. This is a very sad occasion. I’m going to be crying into my cocoa tonight.”

William Healing, a divorce lawyer working mainly for French clients in London, was relieved his EU citizenship was secure: his mother was French and he has two passports. But it didn’t stop him being angry.

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“This train feels like its going to turn into a pumpkin under the Channel,” he said. “We just have no idea what we’re heading into. People are going to wake up next January and say, ‘Oh, but I didn’t know this would change, or that.’ We’re going to look back on this whole thing one day and marvel at what we did. It’s madness.”

Queuing earlier in the day at the Gare du Nord, Claire Booth, 45, a day nursery manager from Lincoln, said she was “just gutted”. Returning from Paris with her partner, Mark, 46, from seeing the Birmingham indie rock band Editors in concert, the couple said the uncertainty was the worst.

“It’s the unknown,” said Mark. “I mean, what will Brexit actually look like? After three years, it’s staggering that we still don’t know.” Hours before Britain was due to formally leave the EU, said Claire, “no one can actually envisage Britain being better off because of Brexit”.

Glenn Berry, 34, was returning to London from the Paris Fintech Forum, a big annual event in the financial technology world’s calendar. He wondered how painless the same journey would be in 2021.

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Beyond the possible hurdles to travel, he said, Brexit was already disrupting his professional life: “My company is moving its head office to Amsterdam. Some are going to Luxembourg. We know regulations will change; we just have no idea how.”

But the deeper disruption was emotional. “All my life, I’ve had a European identity; I’ve been lucky enough to have options,” Berry said. “Obviously, we’ll still be a part of Europe on some level. But it feels like we’re saying goodbye to a part of what we are.”

French nationals taking the train were equally downbeat. “This is obviously a momentous day, a terribly sad day; you’re abandoning this project after nearly 50 years,” said Natalie Delassalle, 47, a public relations executive who takes the Eurostar twice a month for meetings in London.

“Honestly, I can’t see why you’re doing it. I don’t understand. I don’t envy you – and not just the passport hassle. You’re on your own now, and the world feels like quite a hostile place. Good luck.”