Britain has funded English language teaching (ELT) initiatives in developing countries for decades, despite changes in government and a series of substantial overhauls in the administration of development aid. This article reveals the relevance of ideational factors in explaining how ELT remained a key part of Britain's aid policy during a period of significant domestic and international change. It uses constructivist institutionalism to interpret an extensive range of evidence from government archives spanning a twenty-two year period (1964-1986). It sheds light on how and why certain ideas become normalised and institutionally embedded over time, and become the cognitive template through which key actors form policy preferences.