The rally is beginning in Pall Mall, central London, earlier than transferring to Parliament Square
Campaigners are gathering in central London to demand a last vote on any UK exit deal.
Thousands of persons are anticipated to be a part of the march to Parliament, on the second anniversary of the UK voting to depart the EU.
The organisers, People's Vote, say Brexit is "not a done deal" and folks should "make their voices heard".
It comes as senior Cabinet ministers insist the UK is ready to stroll away from talks with out an settlement.
The protest is a part of a "summer of action" by marketing campaign teams designed to enhance stress on Theresa May and Jeremy Corbyn.
World War Two veteran Stephen Goodall, 96, is main the protesters as they head from Pall Mall for Parliament Square.
Speakers on the demo will embody actor Sir Tony Robinson and Gina Miller, who efficiently campaigned to make sure the UK couldn't set off talks on leaving with out the approval of Parliament.
One of the rally organisers, James McGrory from stress group Open Britain, mentioned there needs to be "a choice between leaving with the deal that the government negotiates, or staying in the European Union".
"But the most important thing is that this isn't decided just by 650 politicians in Westminster... Brexit is such a big deal [that] it should include all 65 million of us in the country, and that's why people today are marching for a people's vote," he mentioned.
The UK voted to depart the EU by a margin of 51.9% to 48.1% in a referendum held on 23 June 2016.
Britain is due to depart on 29 March 2019, 46 years after it first joined the European Economic Community, the forerunner to the EU.
The authorities is giving Parliament a vote on the ultimate deal, if one is reached, within the autumnbut it surely stays unclear what is going to occur in the event that they reject it.
Organisers of Saturday's demo say folks "from all walks of life" might be current, demonstrating the "growing popular demand" for one other vote.
Protester Colin Hopkins, 62, from Ipswich, mentioned: "It's actually necessary to say we do not dispute the choice, however the course of and the vacation spot.
"There isn't any agreement on where we want to go with it, even in the government, and we have a right to a second opinion on that."
Leo Buckley, 16, from Hampshire, claimed "Brexit has stolen my future", including: "It is stealing it economically...I will struggle to find employment and be worse off when I do."
Janet Watts, 61, from Suffolk, mentioned she joined the march for her momwho's from Denmark and arrived in Britain in 1953.
"She had her passport stamped when she got off the boat at Harwich, telling her she could stay," she mentioned. "That has been the identical till this referendum occurred.
"I think it is disgusting putting families at risk and putting her through this at the age of 83."
This week, the federal government gave extra particulars on how EU residents can apply to keep within the UK after Brexit.
EU residents and members of the family who've been within the UK for 5 years by the top of 2020 might be in a position to apply for "settled status", which means they'll reside and work within the UK indefinitely.
Meanwhile, International Trade Secretary Liam Fox has mentioned Theresa May is "not bluffing" over her risk to give up negotiations.
He informed the BBC it was within the pursuits of each side to have a dealbut it surely was "essential" the EU understood that the UK may stroll away if the phrases provided weren't ok.
"The prime minister has always said no deal is better than a bad deal," Mr Fox mentioned in an interview with the BBC's political editor Laura Kuenssberg.
It was recorded on Wednesdayearlier than Friday's warning from Airbus that it'd stop manufacturing within the UK in such a "no deal" situation.
Liam Fox says Theresa May shouldn't be bluffing over no-deal Brexit
Brexit Secretary David Davis informed the Daily Express the prime minister was going to get a "good deal" from Brussels and Brexit was going to be "fantastic".
"The best option is leaving with a good deal but you've got to be able to walk away from the table," he mentioned.
And writing within the Sun, Foreign Secretary Boris Johnson warned the prime minister not to permit "bog roll Brexit" that's "soft, yielding and seemingly infinitely long"calling for a "full British Brexit" as a substitute.
Mr Johnson mentioned folks "just want us to get on with it".
Labour mentioned Mr Fox's feedback about a no-deal Brexit had been the "height of irresponsibility".
"The next time Liam Fox parrots the slogan no deal is better than a bad deal he should give some thought to the 14,000 people who work for Airbus, and the thousands of other people who have jobs dependent on trade with Europe," mentioned shadow Brexit minister Jenny Chapman.
Both the prime minister and Labour chief have rejected calls for one other public vote, saying the need of the folks expressed within the 2016 poll was clear, though many Labour MPs now need one other referendum.
Anti-Brexit campaigner Femi Oluwole needs the Labour chief to again calls for a referendum on the ultimate deal
Conservative MP Peter Bonewho helps Brexitmentioned if there have been a second vote, the depart marketing campaign would win once more.
"The vast, vast majority of people, whether they are Leavers or Remainers, just want us to get on and come out this dreadful European Union super-state," he mentioned.
"There were 17.4 million people that voted for leave and if there are a few thousand in London complaining about itthat doesn't seem to really make much difference."
The authorities is giving Parliament a vote on the ultimate deal, if one is reached, within the autumnbut it surely stays unclear what is going to occur in the event that they reject it.