Chuka Umunna’s TiG hailed the news of one million voters at the march
Demonstrators calling for a second Brexit referendum later packed out Parliament Square, with rally hosts Mariella Frostrup and Richard Bacon telling them an initial count of demonstrators showed that the amount of people taking part in the march has topped one million, which if true which would eclipse the estimated 700,000 who attended a similar rally in October.
Large screens dotted along Whitehall told people how to text and tweet their support for the Put it to the People march.
Music was being played across the square where thousands of people gathered.
On a small stage on Whitehall, a group of people sang songs reworded with anti-Brexit lyrics.
A placard pokes fun at Prime Minister Theresa May
Travel chaos was reported as overcrowding caused stations to be shut down or made exit only.
The banner stunt was organised by a group calling itself the “Left Bloc” which is supported by Labour MPs, including Clive Lewis and Kate Osamor, Green Party MP Caroline Lucas, trade unions and grassroots campaigners.
In Parliament Square, Labour’s deputy leader Tom Watson is expected to tell marchers that the only way to resolve the Brexit impasse is “for people themselves to sign it off”.
Scottish First Minister Nicola Sturgeon, former deputy prime minister Lord Heseltine and London mayor Sadiq Khan are also expected to take the stage.
Other speakers will include former Conservative cabinet minister Justine Greening and former attorney general Dominic Grieve, former Tory turned independent MP Anna Soubry, Lib Dem deputy leader Jo Swinson, Green Party MP Caroline Lucas and SNP Westminster leader Ian Blackford.
Campaigners are arriving to the capital from across the country, with one taking on a 715-mile journey on ferries, trains and buses from Orkney in Scotland.
Student Sorcha Kirker, 27, will be joined by about 30 other students from the University of the Highlands and Islands.
An EU supporter shouts slogans during the march
Labour’s London Mayor Sadiq Khan tweeted a video of the countdown launching the Put it to the People march, with the London mayor holding up a banner at the front of demonstrators.
He wrote: “And we’re off!
“Here in London, thousands of people from across our city and country have come together with @peoplesvote_uk to send a clear message: Enough is enough – it’s time to give the British public the final say on Brexit. £PeoplesVote £PutItToThePeople.”
The banner is unfurled on Westminster Bridge
Green Park and Marble Arch were just two of the stations tube drivers refused to stop at due to the hoards of demonstrators.
The pandemonium at Green Park was compounded by someone pressing the emergency stop button on the escalators, according to one irate conductor.
Traffic on Oxford Street backed up as protesters spilled into the road on their way to Park Lane, where the march started at 1pm, amid a jovial atmosphere.
Marchers in central London head for Parliament Square
Millie Hill from Gloucestershire told Express.co.uk: “I hate everything about Brexit. I don’t want to be the old Britain. I want to be open.”
James Hyson from Hampshire added: “I believe in the solidarity of people and I attribute the peace and prosperity of the last half century to the Union.”
Riley Alexandre, part of a group of students Pride Society from Falmouth and Exeter University: “I was 17 when the referendum happened and never had a chance to vote. We were never asked and it’s our future that will be affected.”
Celebrity chef Delia Smith at the march
The Independent Group tweeted a video of their MP Anna Soubry from the Put It To The People march, cheering when the organisers claimed that 1,000,000 people were in attendance.
Alongside the video posted on the parliamentary group’s official Twitter, they wrote: “We’ve just heard how many people have come along to the £PutItToThePeople march in London today!
“Incredible support from people along the route too. Thank you. £ChangePolitics.”
An EU supporter dressed in costume on her way to the march in central London
The London march coincides with pro-Brexit campaigners continuing their long hike from the North East to the capital.
Former Ukip leader Nigel Farage re-joined the March to Leave when it set off from Linby, near Nottingham, on Saturday morning.
Saturday’s demonstrations follow EU leaders agreeing to delay Brexit to give Prime Minister Theresa May a final chance to get her deal through Parliament.
Leaders agreed to extend Brexit to May 22 if Mrs May can get MPs to back her deal in the Commons at the third time of asking.
One million people could join the march, estimates suggest
If the vote is not passed, the UK will have to set out an alternative way forward by April 12, which could mean a much longer delay – with the UK required to hold elections to the European Parliament – or leaving without a deal at all.
An online petition demanding the Government stops the Brexit process had topped four million signatures by Saturday morning.
The march is happening on the same day a petition calling for the revocation of Article 50 has soared past the four million mark.
Bookmakers have slashed the odds of the petition hitting five million by midnight, as well as the chances of Article 50 being revoked by the end of the year.
Independent Group MPs Chuka Umunna and Anna Soubry pose for a selfie
Anna Soubry celebrates the news of a million marchers
William Hill cut the price of the petition reaching 5 million votes by midnight to 5/4, down f from 5/2.
Meanwhile it is 2/1 that Article 50 is revoked before the end of the year.
William Hill spokesman Rupert Adams said: “As of 9.20 this morning the Petition has hit 4 million and we believe it has a great chance of getting to 5 million today.
”Seeing the support we might just have to trim the price of Article 50 actually being revoked.”
(Additional reporting by Katie Whitfield)