Boris Johnson’s Brexit offer to the EU is not dead on arrival – but it may well be dead within the next 48 hours.

And that could become clear as Michel Barnier, the EU’s chief negotiator, briefs EU ambassadors and MEPs about what he sees as the deficiencies of the proposals.

The biggest hole, as you would expect, is that EU government heads are being asked to take on trust that all the legal and technical preparations necessary for checks on goods and food flowing from Great Britain to Northern Ireland, and all the legal and technical preparations for customs checks away from the...