A couple of days before the referendum, Theresa May noted that if Britain had a different regulatory environment from the EU there would have to be a hard border on the island of Ireland. She was right.

The trouble is that, once in No10, she announced that leaving the EU must also mean leaving the single market and the customs union. As a result, the border question has inevitably taken centre stage.

Ministers have promised again and again that there will be no return to a hard border. But they have still not produced any even half-baked solution. There is no “virtual border” customs arrangement anywhere in the world.

As with so much of their approach to Brexit, they are big on promises but the