Three years ago, I was having lunch in an Italian restaurant with the leader of Belgium's Flemish nationalist party, Bart De Wever. "Give me Elio Di Rupo as prime minister of Belgium and then make Prince Philippe a king," the head of the New Flemish Alliance told me. "Within five years Belgium will be finished. Game over." At the time I took it as a joke, or perhaps some braggadocio from a man who might have become somewhat detached from reality following the huge success of his party in the 2010 elections. Three years later, it turns out Mr. De...