Published: 5:41 AM March 23, 2019 Updated: 8:42 AM September 18, 2020

Hundreds of thousands took part in October's People's Vote march. (Photo by Wiktor Szymanowicz / Barcroft Media via Getty Images) - Credit: Barcroft Media via Getty Images

Hundreds of thousands of people are heading to London today to march on parliament calling for the public to be given a final say on Brexit.

Demonstrators will flood into the capital from across the country for the Put It To The People march in Parliament Square.

The number of marchers calling for a second referendum could soar to more than one million after estimates for a similar rally in October were as high as 700,000.

Campaigners will march from Park Lane to Parliament Square from midday, followed by a rally in front of parliament.

Labour's deputy leader Tom Watson will tell crowds that he has reluctantly come to the view that the only way to resolve the current impasse is 'for people themselves to sign it off'.

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Watson will tell the crowds in Westminster: 'The current impasse is not working for people who voted to leave or people who voted to stay. I really don't think Parliament will be able to resolve this.

'That's why I've come to the reluctant view that the only way to resolve this and have legitimacy in the eyes of the public is for the people themselves to sign it off.

'It can only bring closure if we're all involved in making the decision.'

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Scottish first minister Nicola Sturgeon, former deputy prime minister Lord Heseltine and London mayor Sadiq Khan will also address the protest.

Other keynote speakers 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 will pour into London from across the country, with one embarking on a 715-mile journey on ferries, trains and buses from Orkney in Scotland.

Student Sorcha Kirker, 27, is the vice president for higher education of the Highlands and Islands Students' Association, and studies archaeology at Orkney College UHI.

She said she will be joined by about 30 other students from the University of the Highlands and Islands.

She added: 'Personally I think it's really unfair because predominantly students and young people don't want Brexit, and many were not old enough to vote in 2016, yet we are the ones whose futures it will affect for the longest.'

The march comes on the same day pro-Brexit campaigners will continue their long hike from the North East to London, with former UKIP leader Nigel Farage re-joining the March to Leave when it sets off from Linby, near Nottingham.

Fewer than 300 people turned out to meet Farage on the first day of his pro-Brexit march last weekend.

A petition calling on the government to Revoke Article 50 had passed three and a half million signatures on Friday evening.