A fairly large proportion of those Norman castles which may be considered to have been built for coast defence, have been constructed in such a way as to take advantage of pre-existing Roman castra. Porchester is an admirable specimen. Here the north-western portion of the Roman enclosure has been cut off by Norman walls so as to form the inner bailey, whilst the remainder has been converted into the outer bailey. Pevensey, London, Rochester, Colchester, Cardiff and Lancaster are other excellent examples. In passing, it may be noted, that at Reculver and Porchester, the parish church has been built, doubtless for safety, within the walls of the castrum; whilst at Pevensey two parish churches have been erected sufficiently near the castrum to suggest that the sites were selected with a view to securing protection. The regular castles of masonry erected during the reign of Henry II, a great castle-building period, although very important as military works, were not in the main built for the defence of the coast. But it is necessary to bear in mind that in ancient times river-courses, even far from the sea-coast, were subject in a peculiar degree to the incursions of the enemy, and the great Norman keeps of Canterbury, Rochester, and the White Tower of London, although situated far from the sea-coast, played an important part in the defence of the coast. At Porchester, Pevensey, Hastings, Folkestone and Dover, the relation between the Norman castles and the coast defences was much more intimate. PART III MEDIAEVAL CASTLES AND WALLED TOWNS ON THE COAST MEDIAEVAL CASTLES AND WALLED TOWNS ON THE COAST In the following account of the more important of the castles which in mediaeval times guarded the coast, it has been found convenient to include a notice of those walled towns with which, in many cases, they were closely associated. The mediaeval castle, generally speaking, represents an effort to maintain the power of the feudal lord, and, in a lesser and secondary degree, provision for resisting raids and invasion by foreign enemies. Walled towns, on the other hand, when situated on or near the coasts, or on navigable rivers, were primarily designed for coast defence. The mediaeval castles which were built in situations remote from the coast were the fastnesses and strongholds of nobles fighting amongst themselves or against the king. In the following accounts of the more important examples of castles and walled towns wholly or partially designed for the defence of the coast, occasion will be taken to point out the interesting series of developments through which these mediaeval fortifications passed as time went on. For example: