On May 29, France will hold a referendum on the European constitutional treaty. I believe the odds still favour ratification. But since the last five opinion polls before the weekend put the No vote ahead, it is perfectly legitimate to ask what would happen if the French voted this way.

One would have thought Europe's political leaders had a contingency plan to deal with this kind of emergency. But, at least to my knowledge, no such plan exists. As one senior European Union official put it recently, the consequences of a French No vote were "too awful to contemplate". As a result, few EU officials have contemplated them.