Now, getting rid of the backstop is essential. If activated it would tip the UK into an arrangement worse than EU membership. We’d be bound by EU rules and institutions with even less control over them than we had before. This would reduce Britain to the status of an EU colony, all for the sake of avoiding a ‘hard border’ that Ireland, the EU and the UK all do not want, and which all parties have promised never to erect.

But what is more significant about Johnson’s letter is what it didn’t mention.