The battle has been lost, but hard-line Remainers believe the war can still be won.

Already, pro-EU activists are trying to mobilise supporters to campaign for Britain to rejoin the European Union.

Although Brexit has yet to be completed, Remainers now accept it will be, after Boris Johnson's emphatic election victory.

But some are convinced British voters can be persuaded to opt to rejoin the EU at some point in the near future.

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Dozens of social media groups are being set up around the country to galvanise a grass-roots Rejoin movement.

Mike Galsworthy, the founder of Scientists4EU, wrote on Twitter: "The majority of people will have voted for pro-People's Vote parties. Brexit may have a parliamentary majority now, but it has a popular minority. Poll after poll shows a popular preference for Remain. That's a huge community to work with. We must focus on building up our communities all over the UK. First thing to do is just know we have huge community of local pro-EU groups on social media."

Urging people to join pro-EU social media groups he added: "We're fighting for British European values. Rejoin may be a long game — but in the short run we need to fight off a crash out and sell-out to Trump. It'll be a battle."

Writer Anita White, wrote: "Boris Johnson has taken responsibility for the whole Brexit mess.

"When the electorate finally wake up to this they will destroy him and his party."

The Rejoin push comes after the People's Vote campaign, which had pushed for a second referendum on Brexit, accepted defeat and announced its dissolution.

Open Britain says it will now "refocus" to campaign on "vital social issues" and will "rebrand" next year to push for a "fair deal for Britain".