In The Art of The Deal Donald Trump argued that the secret of success was to “play to people’s fantasies”. The trick, he wrote, is to present the biggest and most spectacular version of your product; he called it “truthful hyperbole”. You can only push it so far, though. “You can’t con people, at least not for long. You can create excitement, you can do wonderful promotion and get all kinds of press . . . but if you don’t deliver the goods, people will eventually catch on.”

This is what Theresa May and Jeremy Corbyn must remember as the cross-party talks on Brexit resume today.

The prime minister and the Labour leader both claim that the message of the local elections was that politicians