Nationalism has long been a dirty word in Europe’s polite political circles. Many politicians still bristle at the term. Nationalism was the destructive fever that drove the continent mad in the first half of the 20th century and flared up again in the Balkans in the 1990s with murderous results. “Nationalism is war,” said François Mitterrand, the late French president.

Europe’s greatest postwar achievement has been to dilute that nationalist poison so as to make war unthinkable. Sovereignty was pooled in the European Union, the “most effective conflict-resolution mechanism ever devised,” according to George Schöpflin, a historian of European nationalism and Hungarian MEP.