What if they succeed in thwarting Brexit? The odds seem weighted against Boris Johnson delivering his do-or-die (-in-a-ditch) promise to get the UK out of the EU by Halloween. The Benn Act has tied the government’s hands so there is no need for Brussels to budge. Donald Tusk can wait until Johnson cracks and complies, or until the Remain Parliament ousts him and installs a prime minister who will hold a second referendum or revoke Article 50 altogether.