At Park Lane, one million people are gathering to march in support of a “People’s Vote”. Europhiles walk around draped in flags and waving signs that say “Don’t stop the mEUsic”, “Fromage not Farage” and “Time for an EU-turn”.
Belgian-born animator An Vrombaut is pumping helium from a canister into the balloons that are attached to her cardboard replica of Big Ben.
“Oh God, I’m smoking a cigarette,” says another protester on seeing the canister.
“It’s not flammable!” says Vrombaut.
She's here today with another Belgian, NHS employee Bie Grobet, and other members of In Limbo, a group for EU citizens based in the UK. In Limbo has produced two books of testimony from EU citizens in the UK and UK citizens in the EU about their fears and worries about their statuses post-Brexit.
“Brexit was like a rug being pulled from beneath you,” says Grobet.
Nearby, Stuart Thomson and Cathy Ellison are gathering with other Veterans for Europe. Thomson wears three medals, for "Kurdish famine relief, the first Gulf War and Bosnia". Ellison has even more medals than Thomson, including one from the last Iraq War.
“You can’t beat a good march,” says Thomson. “A lot of Remainers say, ‘I didn’t know the military was on our side’.”
“It’s frustrating,” says Ellison. “There’s this notion that all of the military are against the EU and that Europe is the enemy, but these are countries we’ve worked alongside for years.”
"These ridiculous things you see online about England saving Europe during the second World War," adds their friend, fellow veteran Peter Flynn. "We fought among the Danish, the French, the Poles. It was a Polish squadron that shot down most planes in that war."
"Brexit is the single most cowardly thing this country has done," says Thomson. "You don't abandon your friends. Look at what Putin is doing . . . Look at that fool in the White House. Now is not the time to abandon our allies."
There are a lot of idiosyncratic political niches here. Jordan Barry is a member of Tories against Brexit* as well as a group called Remainer Now. The latter group is for former Leave voters who have changed heart. Barry was a Leave supporter but he says that since then he has learned a lot about how the EU actually works and become fully aware of the problems with the Irish Border.
He wrote a piece for a publication called the New Federalist explaining his change of mind. “I was never against immigration,” he says. “But I got caught up in the idea that we weren’t sovereign anymore.”
A man is playing Ode to Joy, the EU anthem, on a kazoo, and I see signs that read: "Don't make me stockpile French cheese", "Theresa May can f**k off back to that field of wheat" and "#freelaurakuenssberg" (Laura Kuenssberg is the Brexit-imprisoned political editor of BBC news).
Bo Fowler is dressed as an astronaut and holding a sign that features a model of Mars and the words: “If we leave the EU, I’m moving to Mars.” “I’m half-serious and half-not-serious,” he says. “Escaping to a planet with no politicians seems like a good deal to me. And maybe Mars will join the EU in a few years?”
He's thought about this a lot. He's currently writing a philosophical, non-fiction book that uses moving to Mars as a metaphor for free thinking. He says he's heartbroken by Brexit. He is half-American and he's an internationalist at heart. "It's a Tory civil war made national," he says. "The worst crisis since the Suez. "
Everyone cheers when a helicopter passes overhead and everyone boos as they pass Downing Street. At Parliament Square, we strain to hear speeches from politicians like Tom Watson, Nicola Sturgeon and Anna Soubry and entertainers like Sandi Toksvig and Siobhán McSweeney, who plays Sister Michael in Derry Girls (she thanks the protesters for supporting the people of Northern Ireland). At one point, people start chanting "Louder! Louder!" as London mayor Sadiq Khan speaks rather inaudibly. The atmosphere is festive, although one older man mutters, with disapproval: "It's a protest, not a pop concert."
Before I leave, I speak to a man in a devil mask who is posing beside grotesquely fleshy effigies of David Davis, Michael Gove, Boris Johnson and Theresa May in hell. He's with a group called the EU Flag Mafia and the effigy was created by Jacques Tilly. The man in the devil mask says I can call him "Karl". He can't give me his real name because "I work for a certain public broadcaster who wouldn't be pleased".
Why is protesting so important to him? "The European Parliament isn't perfect but outside it we can't influence anything and are prey to bigger global powers." He also worries that Brexit could be the start of something much darker. He tells me his family experienced the worst of the Holocaust. "I know how to recognise the stench of fascism."
*This article was edited on March 25th, 2019