Federica Mogherini, who spent years as the European Union's chief diplomat and human rights champion, has been arrested as part of a Belgian corruption investigation. The charges — procurement fraud, conflicts of interest, and violation of professional secrecy — are exactly the sort of institutional rot she was nominally positioned to help Europe lecture other countries about.

The arrest marks a spectacular descent for one of Brussels' more recognisable faces, whose post-EU career involved leading a prestigious academic institution. Prosecutors allege that somewhere between the idealism and the institutional prestige, financial impropriety found a comfortable home.

The case is a gift to every government that has ever sat through an EU delegation's anti-corruption presentation. It also raises the obvious structural question: if the people tasked with projecting European values abroad cannot clear a basic ethics bar domestically, what exactly is being exported? Brussels will presumably respond with a strongly worded statement and an updated code of conduct.