It had been called the dinner party from hell. A seven-strong convention of the also rans. But only one dinner guest really mattered: Nigel Farage. The populist politician’s last-minute decision to stand as a Reform candidate in Clacton has struck fear into the hearts of Conservative MPs across the country, but especially in the 60 marginal seats that Professor John Curtice says Reform could help the Tories lose on 4 July.