Handling Brexit was never going to be easy for Theresa May, given that the Tories have been fighting a civil war over Europe for at least a quarter of a century. But the past ten days have been so calamitous that there is a real possibility that her Chequers gambit — threatening a general election unless MPs support her watered-down version of Brexit — could lead to the fall of the government and the ceding of power to the most left-wing Labour administration in history.