Most people wear their politics lightly, like favourite items of clothing to be adjusted slightly in colour and trim as the fashions alter. They don’t really understand those who keep their ideologies like old Mormon underwear: unchanged, close to the skin and on at all times.

So it is with many bright new Labour members, who sunnily signed up to the Corbyn project and today find themselves wondering why he doesn’t share their view of Brexit. But now it’s crucial: what, exactly, does Labour want?

The most popular explanation in Labour circles for Jeremy Corbyn’s vagueness on the issue has been “constructive ambiguity”. I never liked it but cleverer people than me said it was a canny strategy, borne out by the polls.

In this