The half-century habits of Franco-German condominium die hard. It is a painful process for French elites to admit that monetary union is asphyxiating their economy and must inevitably trap France in mercantilist subordination to Germany. The Carolingian union is all that anybody in French public life can really remember. It worked marvellously for two generations, levering French power on the global stage, and the euro was of course their own creation, intended to tie down a reunited Germany with “silken cords”. How can they now face the awful truth that this elegant strategy has blown up in their faces, enthroning...