The growth of the study of English artillery fortification, coupled with the various inadequacies of B.H. St J. O'Neil's Castles and Cannon, mean that a reappraisal of these defences is long overdue. The scattered evidence, both architectural and documentary, for pre-1539 works is brought together to form a background against which studies of individual sites may be made. The emphasis is on castles, town defences and blockhouses, but there is a separate section relating to fortified manor-houses.