This chapter periodises the British historiography of international law in five parts. Its first period extends from Robert Ward’s Enquiry into the Foundation and History of the Law of Nations in Europe (1795) to Thomas Erskine Holland’s Oxford inaugural lecture on Alberico Gentili (1874), and traces the gradual professionalisation of the discipline and its historical strain. The second part examines the entanglement of empire and historicism in British international legal historiography from around 1870 to roughly 1920. The third part treats the symbolic coming of age of British international legal historiography, between the founding of the British Yearbook of International Law in 1920, and Hersch Lauterpacht’s pivotal enunciation of the so-called ‘Grotian’ tradition of international law after the Second World War. The fourth part explores the history of international law in the succeeding ‘age of Lauterpacht’ up to c. 1960, when historiographical advances came increasingly from the semi-periphery rather than the centre and from disciplines other than international law. The fifth part takes stock of the transdisciplinary ‘turn’ to the history of international law in the British world and the chapter concludes with reflections on the nascent field of comparative international legal history in the light of British developments over the longue durée.