This article (originally given as the Annual War Studies Lecture at King's College, London, on 25 January 2010) challenges the assumption that Britain's relationship to genocide is constituted by its `vigilance towards the genocide of others. Through a critical overview of the question of genocide in the historical and contemporary politics of the British state and society, the article suggests their wide-ranging, complex relationships to genocide. Utilising a conception of genocide as multi-method social destruction and applying the interpretative frames of the genocide literature, it argues that the British state and elements of identifiably British populations have been involved directly and indirectly in genocide in a number of different international contexts. These are addressed through five themes: the role of genocide in the origins of the British state; the problem of genocide in the Empire and British settler colonialism; Britain's relationships to twentieth-century European genocide; its role in the genocidal violence of decolonisation; and finally, Britain's role in the genocidal crises of the post-Cold War world. The article examines the questions of national responsibility that this survey raises: while rejecting simple ideas of national responsibility as collective guilt, it nevertheless argues that varying kinds of responsibility for genocide attach to British institutions, leaders and population groups at different points in the history surveyed