Postcolonial analyses of the construction of ‘otherness’ have enabled an enhanced appreciation of the cultural dynamics of imperialism. However, some postcolonial work has been characterized by an unhelpful degree of abstraction. Within geography, as within other disciplines, the postcolonial perspective has also suffered from a restricted metropolitan focus. Based on a study of the connections between official, settler and humanitarian discourses within the Cape Colony on the one hand, and metropolitan political discourses on the other, this paper sets the metropolitan construction of racial difference in a wider context informed by developments at the periphery of empire. It also establishes some of the ways in which constructions of racial ‘otherness’ influenced British spatial strategies on the early nineteenth-century imperial margins.