Tens of thousands of anti-Brexit protesters have travelled from all over the country to London for the 'Put it to the People March' as the online petition urging the government to cancel Brexit passed four million signatures.
Opponents of Britain's departure from the European Union began gathering in Hyde Park from 12pm before converging on Westminster.
Speakers set to address a rally outside Parliament include Scotland's First Minister Nicola Sturgeon, London Mayor Sadiq Khan and opposition Labour deputy leader Tom Watson.
'Brexit is a complete and utter mess,' Khan said on the eve of the event.
Thousands of people gathered in Hyde Park from 12pm before converging on Westminster to take part in the Put It To The People march
Trains, coaches and buses were chartered to bring as many people as possible, from all around the country to today's anti-Brexit march in London
EU supporters, calling on the government to give Britons a vote on the final Brexit deal or reverse Brexit entirely, descend on the capital to protest
An anti-Brexit protester carries his child on his back during today's protest, while she holds up a sign saying 'May I have my future back please'
'I'll be marching on Saturday with people from every part of our country - from every walk of life - to demand that the British people get the final say.'
Earlier, former Ukip leader Nigel Farage joined the counter March to Leave in Linby, Nottinghamshire, telling around 200 Brexit supporters that Theresa May had reduced the nation 'to a state of humiliation'.
The 'People's vote' protest - set to be one of the largest in the capital in decades - is hosted by the People's Vote pressure group.
Saturday's protest follows a similar demonstration in October that drew an estimated half a million people.
Organisers have arranged hundreds of coaches and even chartered a train to bring protesters from all corners of the country to the capital.
Among those planning to attend is Stephen Goodall, a 96-year-old World War II veteran, who will travel 200 miles by train from southwest England alongside four generations of his family including his great-granddaughter.
Organisers have arranged hundreds of coaches and even chartered a train to bring protesters from all corners of the country to the capital