“National identity” is one of those concepts, like “political culture”, which historians have somewhat casually borrowed from the social sciences and then used promiscuously for their own purposes. Over twenty years ago Philip Gleason wrote a wise and prescient (yet sadly underappreciated) essay on the origins of the concept of “identity” in the 1950s, warning historians that already then it had two quite distinct—psychological and sociological—meanings that needed to be distinguished to retain any conceptual clarity. Since then our own use of it has proliferated uncontrollably, and the original confusion identified by Gleason has been compounded by many others. The chain of communication between the concept's progenitors and its present-day users is now so long and so fragmentary that our usage may bear little or no relation to the discourse that Gleason described. There may be nothing wrong with this state of affairs; historians may have found their own value in the term, which need not necessarily be validated by social science. Yet social scientists have continued to work with “identity”, and have puzzled much further over its possible meaning and utility with a degree of conceptual rigour that historians do not usually share. And we continue to validate our own use of the term by reference to an increasingly shadowy and distant social science whence it came. Accordingly it may be useful to look more closely at what social scientists think “national identity” is, and how it operates in human minds and societies. This essay attempts a brief exploration of that kind and then applies its findings to the recent historiography of “national identity” in modern Britain.