Over the course of the last few decades, the European legislature has adopted a total of 18 Regulations in the area of private international law, including civil procedure. The resulting substantial legislative unification has been described as the first true ‘Europeanisation’ of private international law, and even as a kind of ‘European Choice of Law Revolution’. However, it remains largely unclear whether the far-reaching unification of the ‘law on the books’ has turned private international law into a truly European ‘law in action’: To what extent is European private international law actually based on uniform European rules common to all Member States, rather than on state treaties or instruments of enhanced cooperation?