'I live in Flanders and I study in Brussels and I am marching against separatism because I don't want it and nobody I know wants it. We live in one country. Some politicians are intent on pushing us in a direction we do not want to go and I am here because maybe people will see this on television and understand that they too can protest and change things,' said Pierre van de Walle, 21.
The protest was billed as 'a chance for the silent majority to voice their dissatisfaction with the way politicians are ruining the country', and for two hours a stream of people poured down the north-south axis of the city, cheering good-heartedly in French and Flemish.
The crowd, from all over the country, was predominantly young and well-heeled, peppered with war veterans, who drew a huge cheer, and social and cultural organisations. Astride parental shoulders two children wearing masks - one the cock that is the symbol of French-speaking Wallonia, the other the lion that is the symbol of Flemish-speaking Flanders - held hands.
The march, whose student organisers had tried to make apolitical, none the less attracted the support of leading MPs, and national heros such as Eddy Merckx, the greatest champion the cycling-mad Belgian nation has known.
On Friday, that old-style nation formally ceased to exist when parliament approved the remaining articles of a constitutional reform to create 'a federal state composed of Communities and Regions'. The reform, set in train and agreed only after months of wrangling, is the end of a long battle to make explicit the desire for regional autonomy that has set the rich Flanders region in the north against southern Wallonia and the might of bilingual Brussels.
For an influential minority of Flemish politicians, a federal state is the first step to complete separation: the Czechoslovakisation of Belgium. For Flanders, once the poor relation but now the wealthiest part of country, is tired of paying for Wallonia and convinced it could go it alone.
But Belgium, now the EC's most heavily indebted member, is slipping into recession. More than ever, the federalists argue, the country must pull together. But the near-failure last month of the Socialist-Christian Democrat coalition to agree an austerity budget highlighted the fragility of political relationships and prompted public exasperation that, while the politicians play with federal models that give the regions budgetary and fiscal autonomy, the problems of unemployment and a weakening economy go unsolved.
Many feel their politicians, who are already unpopular, have set the country on an uncertain path for which they have no mandate. Some 163,000 people have signed a petition demanding a referendum on constitutional reform.