Britain’s agreement to accept Ireland’s demands over Brexit and the border is an expression of its weakness: it can’t even bully little Ireland anymore. And this would have been bad enough for one day. But there was another humiliation in store. Having backed down, May was then peremptorily informed by her DUP coalition partner that she was not even allowed to back down. It is a scarcely credible position for a once great state to find itself in: its leader does not even have the power to conduct a dignified retreat.