This paper offers a contribution to recent debates on European Union (EU) external trade and development policy, with a specific focus on the African, Caribbean and Pacific (ACP) group of countries. The question asked is why the EU encountered such difficulties in the attempt to translate its normative preferences for freer trade and closer economic integration into a series of binding agreements? Drawing on both economic constructivist and historical institutionalist insights, it is argued that the case for reform initially rested on a strong convergence between institutions and ideas, enabling the EU to discursively present desired policy reforms as necessary to satisfy World Trade Organisation trade rules. However, in due course, the institutional dynamics behind the latter began to diverge from the EU's policy preferences and blunt its norm-based argument – thus creating the space for transnational coalitions to, first, question and, ultimately, undermine aspects the EU's trade and development prospectus for the ACP.