Any book about castles should begin by saying what they are, for certainly the name ‘castle’ has been much abused by loose usage in the past and, indeed, still is. In France (significantly, as we shall see) the word château has now long been applied to any large country house of social distinction with or without fortification, and in this country, while all kinds of ancient fortifications are sometimes and wrongly called ‘castles’ (e.g. the ‘British’ Maiden's Castle in Dorset or the Roman Burgh Castle in Suffolk), the true nature of the castle proper, and its origins as a French and, more specifically, Norman importation, were scarcely established before the beginning of the present century, chiefly by Mrs E.S. Armitage in that most fundamental and seminal of books, Early Norman Castles of the British Isles (1912). All societies, it would seem, in all periods including our own, have fortifications and defences of some kind; but also all military organization, and all architecture, reflects the type of society which needs it and produces it. What is it, then, about the castle which is different, which sets it apart from other forms of fortification, and which ties it down to that period of Western society which we (rather absurdly) call the Middle Ages?

Much of the answer lies in correct definition, and the castle is basically a fortified residence, a residential fortress. It is this duality – residence and fortress, domestic and military – which goes far to distinguish the castle from other known types of fortification in the West. Thus, for example, when the great house ceases to be fortified, and the magnates of the land no longer build fortified residences, as happens in England and in France, let us say, from the sixteenth century onwards, then there the history of the castle as a viable institution is at an end, and though many will continue to be occupied and many more will survive at least as ruins until our own day, the great country house, unfortified, takes the place of the castle in succeeding centuries as the characteristic residence of the landed aristocracy and the ruling class.