A claim for damages brought by a group of elderly Africans against the British Government for alleged torture during the Kenyan ‘Mau Mau’ emergency in the 1950s and 1960s led to a demand by the High Court that all relevant documentation be produced. The Foreign and Commonwealth Office (FCO) subsequently admitted the existence of withheld official documents from 37 former British dependencies sent to London at decolonisation. This article examines the FCO's account of the long concealment of the collections and questions of ownership, and documents at the UK National Archives; it outlines British policy towards the disposal of colonial government records prior to independence and notes guidelines about the type of material that should not be passed to successor governments. Documents from the ‘migrated archives’ already made public note an increased emphasis on document security, which clearly fed into policy development. The article includes a brief account of international attempts to outlaw the future removal of documentation from its places of creation, and to establish a framework for the restitution of material so ‘migrated’, with reference to more general current discussions about migrated archives. Questions are raised about the extent to which the new material may add to our historical knowledge, about the utility of its cataloguing for other national archivists who wish to identify gaps in their own holdings, and about the decision to retain the collections in the UK.