This chapter examines the significance of public authority in the British system of government. It seeks, in particular, to explain why the structure of public authority that evolved in Britain did not recognize a formal distinction between public law and private law. Critical to that account, it is suggested, is an appreciation of the ambivalent standing of the concepts of state, constitution, and administration in the British system. The status of these concepts has been placed in question as a consequence of the growth of government, especially over the last century. The dramatic extension in administrative government has unsettled many of the assumptions on which Britain's historic evolutionary constitution has rested and presented certain novel legal challenges. This has resulted in the formation of a centrally-directed administrative system, the emergence of a distinctive system of administrative law, and an explicit acknowledgment of a public law/private law division.