One of the questions asked by this panel is how the internal dynamics of leadership are reflected in the EU’s external ambitions to play a leadership role in world politics. The creation of CFSP and CSDP and related institutions, procedures and capabilities are more than ways of organising the union’s external activity; they also symbolise the EU’s identity, power and status in this particular field. The organisation and workings of CSDP are heavily influenced by NATO, which is the leading security actor, especially when military security is concerned in Europe and an important partner to the EU in security matters. The political stalemate in formal inter-organisational interaction between the two under the Berlin Plus agreement caused by Turkish and Cypriot disagreements has hampered not only EU-NATO cooperation but also led to institutional innovation with implications for the EU’s leadership potential as a security actor. For one, we have seen the emergence of parallel EU and NATO security practices, such as the build up of parallel institutions and capabilities and the launch of individual field operations. In addition, when signals from political decision-makers are blocked by politics, practical solutions are often found on the ground. The paper shows how a range of informal practices, initiated and performed by individuals, also acting in clusters, have replaced formal leadership in headquarters and in military and civilian crisis-management and peace operations. Through these everyday informal or ad hoc practices, a new type of informal leadership performed by diplomats, international political staff and military staff is influencing European foreign policy action, across institutional and national borders. Drawing on practice theory and the logic of practicality, the paper seeks to contribute to a deeper understanding of this particular type of informal leadership and how it may constrain and enable European leadership in security policy.