Leading election expert Sir John Curtice, who correctly predicted the 2016 referendum result, has suggested it may be difficult for  the Conservatives to win an overall majority – and that could spell trouble for Boris Johnson.

“It’s an election that Boris Johnson has to win. If he does not get a majority or something very close to it, he will not be able to stay in government because the Conservatives do not have any friends elsewhere,” he told LBC radio.

“The Labour Party, by contrast, at least has the possibility of doing a deal with the SNP, a deal with the Liberal Democrats, getting support of the Greens and maybe even the DUP not standing in their way.”