At least one million demonstrators flooded the streets of central London as they marched on parliament to demand the public are given a final say over Brexit.
Marchers set off from Hyde Park Corner at around midday on Saturday as part of the Put it to the People protest.
Organisers claimed there was a turnout of around one million, which they said made it one of the biggest protests in British history.
The figure was has been amassed from stewards, staff and volunteers on the ground along the entire march route from Marble Arch to Parliament Square, as well as examining aerial pictures from television helicopters.
Marching bands, music, whistles, chants and cheers provided a noisy backdrop to the march.
Demonstrators wore blue and yellow berets and flew large EU flags above the crowd as the march slowly made its way to Parliament Square.
Placards bore messages urging the government to ‘revoke article 50’ and for Brexit to be put to the people.
The size of the crowd saw people spill over into the capital’s side streets and some underground trains were not stopping at Green Park station.
Mariella Frostrup and Richard Bacon, who were hosting a rally in Parliament Square, told the crowds an initial count showed the amount of people taking part in the march had topped one million.
Many people wore yellow fluorescent stickers reading ‘Bollocks to Brexit. It’s not a done deal’.
The day’s activities were kicked off by the unfurling of a large banner on Westminster Bridge that read ‘Love socialism, hate Brexit’.
The 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 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 also addressed the crowds.
Campaigners arrived in the capital from across the country, with one taking on a 715-mile journey on ferries, trains and buses from Orkney in Scotland.
A spokesperson for the march organisers at the People’s Vote campaign said: ‘It is almost impossible to put an exact figure on the size of this immense crowd because it is spilling out across central London. The start of the march at Park Lane has been filled to bursting point and many thousands of people are trying to make their way to Parliament Square through side streets.
‘At the time the rally began, people were still arriving in Park Lane. Our estimate is based on professional expert advice and whatever the exact number, there can be no doubt that this ranks as one of the greatest protests – possibly the biggest ever – that this country has ever seen. We have no doubt that this march is bigger than the last with our early estimate putting the size of the crowd at around one million.’