If Michel Barnier and David Davis, in their regular dialogue of the deaf, seem to be inhabiting different mental universes, that is because they are. The British and French have often found each other particularly difficult to negotiate with. Of course, Barnier represents not France but the EU, and he has a negotiating position, the notorious European Council Guidelines, on which the veteran British diplomat Sir Peter Marshall has recently commented that ‘I have never seen, nor heard tell of, a text as antipathetic to the principle of give and take which is generally assumed to be at the heart...