All papers are based on the use of archival collections of the Commission and of other actors (national archives, private papers, etc.). Michael Geary will analyse the early years of the complex question of British membership of the EEC by examining the role of the Commission during the enlargement discussion and the subsequent renegotiation. Emmanuel Mourlon-Druol will explore the attempt of the Commission to develop its competences in a new field, banking regulations, with limited success at the beginning. Laurent Warlouzet will examine competition policy, and in particular the merger regulation negotiation, to understand how the Commission managed to progressively centralize the implementation of this field. Billy Davies will provide a transversal vision on a key element: the development of EEC law and the resistance that it triggered. He will explore the vision of the Head of the Commission Legal Service.