If we may use the word ‘librarian’ to refer to the person responsible for the care and administration of a collection of books owned by a medieval institution, we must bear in mind that the role was very different in different libraries. Variation through time is one part of this: while some books from the eighth and ninth centuries might be preserved in the same library for centuries, neither the library nor its use remained constant. Wide variation in book provision is another. Institutions of different kinds kept libraries of different kinds and managed them in different ways. At one level the differences between institutions are obvious. Religious houses such as those of the Benedictines or Augustinians had substantial libraries in many cases, and these might remain substantial over long periods, in some cases changing in their organisation, in others remaining largely unaffected by change over long periods. But similar rules need not imply similar book provision; other houses of the same religious orders might have very minor libraries. Their management would clearly differ, yet one can find evidence of the most advanced librarianship in a quite modest library such as that of Dover Priory, a small Benedictine house dependent on Canterbury Cathedral Priory. Religious orders with a different culture from that of the Benedictines, such as the Cistercians, nonetheless maintained libraries of a similar kind though generally on a smaller scale. With a few prominent exceptions, nunneries were mostly small; their book provision does not run in parallel to that in monasteries for men, however, since the literacy of religious women seems to have declined in the early Norman period, at exactly the period when men’s abbeys were investing in their libraries.