Research in postcolonial geography has overlooked the period, practices and spaces of political decolonization in favour of studies of high imperialism and ongoing contemporary colonialism.Here, I suggest geographers should look more carefully at the mid-twentieth century era during which people, institutions and states negotiated, performed and experienced becoming postcolonial. I make this case by focusing on the modern Commonwealth which emerged from the end of the British Empire, and specifically, on two Commonwealth Heads of Government Meetings in the 1970s. At this time the Commonwealth was an important site for rehearsing anticolonial, anti-British and postcolonial political identities, for contesting British policies in Southern Africa and intervening in ongoing decolonization. The paper makes three broader contributions. First, it highlights the need to grasp the specificities of institutions arising from decolonization, and to take this period seriously as one that was experienced, at least by political elites, as one of dramatic change, characterized by exciting opportunities as well as uncertainty and frustration. Second, it broadens conceptualizations of geopolitical space and action by drawing attention to international conferences as geopolitical events through which political positions and identities were staged and performed. Third, it contributes to (and complicates) notions of the subaltern within postcolonial geopolitics.