An estimated 100,000 marched on Westminster on Saturday to show their support for a referendum on the final Brexit outcome, two years after the initial vote.
The People’s Vote March set off at 1pm and organisers believe it is the biggest Brexit protest so far.
The mass demonstration through the streets of London comes on the second anniversary of the 2016 referendum.
Crowds waving flags and placards filled Parliament Square chanting “We demand a people’s vote”.
Comedian Andy Parsons introduced prominent Remainers on-stage including campaigner Gina Miller and actor Tony Robinson.
Other speakers included Liberal Democrat leader Sir Vince Cable, Tory former minister Anna Soubry, Labour’s David Lammy and Green co-leader Caroline Lucas.
Organisers of the march said at least 100,000 people attended, but police did not provide an official estimate.
Ahead of Saturday’s march Boris Johnson heaped pressure on the Prime Minister to deliver a “full British Brexit”, saying that people would not tolerate a “bog roll Brexit” that was “soft, yielding and seemingly infinitely long”.
Speaking at the rally, Labour MP for Tottenham David Lammy said Boris Johnson’s remarks were “no longer humorous”.
He said: “I think Boris Johnson forgets the dignity of his role and the importance of the livelihoods of ordinary British people.
“The day after that announcement from Airbus I thought his statement was unseemly and deeply inappropriate given his role as Foreign Secretary.”
On Friday, International trade secretary Liam Fox also said the UK was not “bluffing” about being prepared to walk away from talks with Brussels and Brexit secretary David Davis said there is “lots going on” to prepare in case negotiations collapse.
Liberal Democrat leader Sir Vince Cable called the remarks “utterly frivolous and irresponsible” on stage in Parliament Square.
“A bad deal is bad enough … but the idea that people can seriously walk away with the havoc that that’s going to create for most of our industries is deeply, deeply irresponsible.”
During his speech, the actor Tony Robinson said he attended as he had a “deep and abiding love for my country”.
He said: “It’s an old-fashioned and embarrassing word but I am a patriot. I am deeply offended that that word has been hijacked by a few reactionary colonialists over there (gestures at Parliament) who peddle the fantasy of a UK that never existed except perhaps in the imaginations of their nannies and parlour-maids.”
In the crowd Matthew Mann, originally from south Gloucestershire, who moved to the Netherlands in 2016 for work, said: “I’m here to show what a European looks like.”
The IT consultant added: “I’m married to a French wife, I have two children who are dual national, and we live in Holland and are caught up in this administrative mess.”
Elsewhere in the crowd, computer science academic Robert Brady, 62, said: “I have an Italian wife, I work in Cambridge, she works in Rome… I think we’re technically what’s called ‘border workers’.”
He added he thought a second referendum was “almost inevitable” as “demographically, younger people are in favour, they want jobs, they don’t want to sing Elgar”.
Organisers of the march said they are preparing for a “summer of action” to “put MPs under greater pressure so that they reassert their sovereignty over the process and recognise the only way to sort out the mess political leaders have made of Brexit is by offering a democratic People’s Vote”.
Organisers said: “This will focus efforts around key moments in the autumn when MPs will have to decide whether to support a bad deal that is so clearly against the national interest.”