MPs, celebrities and business leaders have launched a campaign calling for a public vote on the final Brexit deal between the UK and the EU.
The People’s Vote aims to unite anti-Brexit groups, with a rally being held in Camden, north London, on Sunday.
Organisers said some 1,200 people were at the event, including MPs from all leading parties.
Both the Conservatives and Labour have ruled out a second referendum.
Actor Sir Patrick Stewart, who backs the campaign, said if people voted to reject the exit deal, the UK would “simply stay” in the EU.
Speaking to the BBC at the event, Labour peer Lord Adonis said: “People want a say… It was a vote in the dark two years ago.
“No-one had any idea what the consequences of Brexit were going to be.”
Green Party co-leader Caroline Lucas, also at the event, reassured attendees, saying: “We’ll do everything we can in Parliament for a people’s vote.
“This issue is far too important to to leave to the politicians.”
Britain voted to leave the EU by 51.9% to 48.1% in June 2016.
The UK will formally cease to be an EU member in March 2019, and the two sides hope to reach a deal by October, in time for it to be ratified by UK and European parliaments.
Sir Patrick earlier told the BBC’s Andrew Marr show that the “terms and conditions” of Brexit were “quite unlike” how they were presented during the run up to the 2016 referendum.
The People’s Vote campaign would argue the public, not MPs, should get the final say on Brexit, he said.
He also said he was motivated by “history and emotion” to want to stay in the EU.
“I’m a war baby and growing up a lot of the world was not good. So the day we joined was one of the most exciting days of my adulthood,” he added.
‘To boldly go’
Also speaking on the Andrew Marr show, Foreign Secretary Boris Johnson responded to the campaign, noting that the people’s vote had already taken place:
“They voted with a substantial majority to leave the EU. We’re now trying to deliver on that mandate from the people.”
Mr Johnson addressed the remarks made by Sir Patrick, who played the role of Captin Jean-Luc Picard in Star Trek: The Next Generation.
“I think we’ll get a great result and we’ll be able to have, not only a gigantic free trade deal with our friends and partners across the channel, but we’ll be able to boldly go to areas we perhaps neglected over the past five years.
Read more: http://www.bbc.com/news/uk