In late November 2012, while Matteo Renzi was making an ill-fated bid for leadership of the Italian centre-left, a young MP from his Democratic Party (PD) piped up on Twitter to remark: "OK, Renzi has quite a lot to learn about foreign policy … He won't make the pass mark, I fear #thirdgrade." When he won the PD primaries the following winter, Renzi – canny as ever – hired his sharp-tongued critic as the party's spokesperson on Europe and international affairs. Once prime minister, he ushered her into the top job at Italy's foreign office. Now, the shoe is firmly...