Win or lose this battle, we will win the war, says Farage

Speaking as votes in the EU referendum were being counted across the country, the leading Brexit campaigner told supporters: “The Eurosceptic genie is out of the bottle and it will now not be put back.”

The first result to be announced in the UK gave only a slender lead of 50.7 per cent to 49.3 per cent for Remain in Newcastle-upon-Tyne, which had been expected to give a more enthusiastic thumbs-up for EU membership.

With no exit polls conducted by broadcasters, a reliable picture of the likely outcome was not expected to emerge until the early hours of Friday, with the final result expected at breakfast time. But the final poll of the campaign forecast a Remain victory by a margin of 52 per cent to 48 per cent.

Meanwhile, Conservative supporters of Brexit including Boris Johnson and Michael Gove wrote to David Cameron urging him to stay on as Prime Minister regardless of the result, as Tories battled to restore a unity riven by weeks of divisive “blue-on-blue” fighting.

Some 84 Leave-backing Conservatives signed a letter to tell the PM: “We believe whatever the British people decide you have both a mandate and a duty to continue leading the nation implementing our policies.”

As well as Mr Johnson and Mr Gove, the signatories included Cabinet-level Brexit backers Chris Grayling, Theresa Villiers and John Whittingdale.

But former Cabinet ministers Owen Paterson, Cheryl Gillan and David Jones, along with influential backbenchers David Davis and Bernard Jenkin, did not sign.

Former work and pensions secretary Iain Duncan Smith, who quit the cabinet weeks before the referendum, did not sign but said he thought Mr Cameron should stay.

The signatories make up around 60% of the 141 MPs who publicly backed Brexit.