King Albert and Queen Paola were invited to Bruges with Luc van den Brande, president of the region of Flanders, and top Flemish officials, to witness the festivities. He seemed to enjoy himself enormously and when the crowd as one rose to sing the Flemish anthem, he joined in, though he didn't seem very sure of the words.
This incensed the French-speaking Walloons. The beef is not so much the song (though why, they are asking, was not the Belgian national anthem played) as the circumstances. This week Mr van den Brande made a speech in Wallonia in which he called for last year's reforms to be taken to their ultimate conclusion.
He argued that a federal state is only a half-way house and that confederation is the way forward. He takes confederation to mean two autonomous states, a German-speaking community and a special statute for Brussels, which has semi-autonomous status.
In standing shoulder-to-shoulder with Mr van den Brande, the King is criticised for tacitly supporting Flemish separatists. Nothing Mr van den Brande said was a surprise, for he has always expressed such views, though many Walloons find his language offensive. 'Thanks to constitutional reforms the Flemish house is now habitable but there are some old bits of furniture left from the time when we lived in a centralised Belgian state' he said.
The Flemish case hangs not so much on politics as on economics. Mr van den Brande's chief complaint is that the Flemish budget carries an unfair burden of the nation's social security costs.
Mr van den Brande's popular appeal has earned him comparison with the Italian Prime Minister, Silvio Berlusconi. Many fear his aim is not a confederation, but outright separatism. Support for independence in both Flanders and Wallonia is growing.