It is an academic truism that enlargement affected the functioning of the European Union and its institutions, and that effects of enlargement are especially noticeable in the Council and its sub-structures. Many researchers expected procedures in the Council to become more intergovernmental and decision-making to become more complicated. However, enlargement also contributed to institutional change in the Committee of Permanent Representatives in quite another—unexpected—way: it strengthened the influence of supranational and “quasi-supranational” actors within the Council, such as the Commission, the Presidency and the General Secretariat, and it made decision-making considerably easier in cases where profound national interests of the newcomers were not directly concerned. Four institutional mechanisms can be identified that contributed to this unexpected institutional evolution: The mechanism of socialization, the mechanism of specific and unspecific reciprocity, the mechanism of lack of interest and the mechanism of presidential impartiality. These mechanisms helped to overcome the cleavage between old and new as well as to uphold the strong and often cited esprit de corps within the Council and its preparatory bodies. The paper analyzes these processes and tries to answer the question: how did these mechanisms contribute to a kind of supranationalization of the Council and its substructures after the last rounds of enlargement? The analysis is based on 51 semi-structured, intensive interviews with experts from the Council General Secretariat and from member states’ Permanent Representations
