London is one of the best recorded of medieval cities. Yet the very bulk of the sources has in the past inhibited systematic enquiry, so that for many periods and aspects of its history the capital remains the unknown element in English urban affairs. The greatest quantity of records concerns property-holding, and one way of making sense of this forbidding mass of information is to reconstitute it in the form of histories of the properties to which it refers. Since the early eighteenth century this way of using urban records has been adopted from time to time in antiquarian studies which have thrown valuable light on conditions in English medieval towns. In particular H. E. Salter's work on medieval Oxford inspired the present author to apply similar methods in a study of Winchester, which is now complete. Winchester pointed the way to London and to a means of remedying our great ignorance of that city.