The editorial board of the European Constitutional Law Review has solicited a number of contributions on presidential elements in government systems in Europe. At the origin of the project are some recent sweeping interventions of heads of state in the political arena. These are notably the (suspensive) veto of the domestic Act implementing the European Arrest Warrant Decision by Czech president Vaclav Klaus and the dissolution, against the will of both the government and the parliamentary majority, of the Assembleia da República by Portuguese president Jorge Sampaio in 2004. They excited our curiosity about the latent ingenuities of systems that we think to understand but of which we know so little.