This week marked the third anniversary of Brexit, and it coincided with a grim verdict from the International Monetary Fund: This year, the British economy will do worse than all of the world’s major economies — including Russia.

Britons know they were conned. According to one survey, a clear majority now believe that leaving the European Union was a bad idea.

There is a remedy that would restore British growth, enlarge the country’s ambitions and return it to a central place in shaping a new world of great power competition. It would, of course, require that Britain return to the European Union.