If not, and the vote is to exit, it will be no good saying afterwards that “we didn’t understand what we were voting for” – the repeated complaint made by eurosceptics about the 1975 Referendum. By then it will be too late.

Boris Johnson, the front-runner to be Britain’s next prime minister, has raised the prospect of a shock for the world’s fifth-biggest economy by pledging to leave the European Union on Oct. 31 without a transition deal if necessary.