As at Pevensey and Porchester, a Norman castle was ingeniously constructed within this castrum by placing the mound towards the north-western corner. Two walls thrown out from this, one towards the western wall and the other to about the middle of the southern wall, enclosed practically a quarter of the whole area in the south-western angle, and formed the inner court, whilst the whole of the rest of the area of the castrum formed the outer court. It is obvious that at the period when this Norman castle was built the Roman walls were sufficiently perfect to afford an effective barrier of defence. OTHER ROMAN COAST DEFENCES The coast to the north of Brancaster, the most northern of the nine regular Roman coast castra, is provided in certain places with defences of Roman date, either in the form of watch-houses, or lighthouses, or fortresses. Professor Haverfield, in a recent lecture on the subject,[12] suggests that such structures once existed at (1) Huntcliffe (near Saltburn); (2) at a point near Staithes; (3) on the high promontory of Peak, near Robin Hood Bay; and (4) on another high headland, called Carrnase, to the north of Filey Bay. Generally speaking, the altitude of the sites of these works suggests their use for watching or lighting purposes rather than for purely military defence. To a certain extent the Roman walled towns of Canterbury, Rochester, Chichester, Colchester, and London, must be regarded as having exercised a share in the coast defence of England, because they were situated on rivers now or formerly navigable, and not too far from the sea-coast to be absolutely without value in repelling invaders. The fact that they were constructed specially for defensive purposes, not only against near neighbours, but also against those unwelcome visitors who, from the remote past, and all through the middle ages, have been attracted by the wealth of England, brings them within the scope of the present essay. For obvious reasons, however, and mainly because of the question of space, it is unnecessary to describe in detail every defensive work which was partially available for English coast defence. PART II THE SAXON SETTLEMENT OF ENGLAND DANISH INCURSIONS AND CAMPS THE NORMAN INVASION OF ENGLAND NORMAN COAST CASTLES THE SAXON SETTLEMENT OF ENGLAND