Dominic Raab, the foreign secretary, could lose a seat the Tories have held since 1910

Two constituents have promised Monica Harding that they will run through the streets of Surrey in swimwear if the Liberal Democrat candidate triumphs in Esher and Walton on Thursday.

One is a lawyer at a FTSE 100 company, Harding says, while the other runs a care home. “I am expecting to win,” she grins. “And it’s set to be very chilly on Friday.”

She hopes to unseat Dominic Raab, the foreign secretary, in a constituency the Conservatives have held since 1910. It would be an extraordinary “Portillo moment”, even more so than the potential defeat by Labour of the former Tory leader Iain Duncan Smith in Chingford and Wood Green.

Raab won 59% of the vote in Esher and Walton in 2017, nearly 23,300 votes