ORGANISERS of a major protest in London calling for a new Brexit referendum are estimating that 670,000 people have turned up for the event.

Activists want a fresh referendum in which Britons can have a say on the final Brexit deal.

London Mayor Sadiq Khan joined students, families, health workers and scores more for Saturday’s march, which ended with a rally at Parliament Square.

Among the protesters was Lord of the Rings actor Andy Serkis, who said he believes there should be a second referendum “now that people are more informed” compared to 2016, when Britons voted to pull out of the EU.

He says “the will of the people doesn’t have to stand still, it’s not an immovable thing that is fixed.”

London Mayor Sadiq Khan said Saturday’s event was a “march for the future” for young Britons, including those who were too young to vote in Britain’s 2016 EU membership referendum, when those who favour leaving the bloc won by 52 per cent to 48 per cent.

The mayor, from the opposition Labour Party, has previously backed mounting calls for a fresh referendum so that the public can have a say on whether they accept Conservative Party Prime Minister Theresa May’s Brexit deal or choose to stay in the EU.

He told the BBC that “what’s clear is that the only options on the table now from the prime minister are a bad Brexit deal, or no deal whatsoever. That’s a million miles away from what was promised Two-and-a-half years ago.”

Prime Minister Theresa May of the Conservative Party has ruled out another public vote on the subject.

Organisers brought in some 150 buses to ferry thousands of activists from across the country to the British capital.

Those in favour of pulling Britain out of the EU won by 52 per cent in the 2016 EU membership referendum. Prime Minister Theresa May of the Conservative Party has ruled out another public vote on the subject.

Britain is scheduled to leave the EU on March 29, but negotiations have been plagued by disagreements, particularly over the issue of the land border between the Republic of Ireland and Northern Ireland border.

It will be the U.K.’s only land border with the EU after Brexit, for Ireland is part of the EU, and Northern Ireland is part of the U.K.

There are growing fears of a “no-deal” British exit, which could create chaos at the borders and in both the EU and the British economies.

May, speaking at an inconclusive EU summit in Brussels this week, said she would consider having a longer post-Brexit transition period — one that could keep Britain aligned to EU rules and obligations for more than two years after its March departure. Pro-Brexit politicians in Britain, however, saw it as an attempt to bind the country to the bloc indefinitely.

“This week’s fresh chaos and confusion over Brexit negotiations has exposed how even the best deal now available will be a bad one for Britain,” said Andrew Adonis, a Labour member of the House of Lords. “Voters will neither forgive nor forget if (politicians) allow this miserable Brexit to proceed without people being given the final say.”