In the reign of Henry also began to be constructed fortified dwelling-houses, embattled and usually moated, but not regular castles. The invasion of the prerogative, under Stephen, led to its enforcement with strictness in the subsequent reigns, but as there were few new castles, it was chiefly in favour of fortified houses that the _licentia kernellare_ was applied for and granted. The earliest extant licence of this character dates from this reign, and about a score altogether appear to have been issued by Henry. Of these, six only were applied for by considerable barons, and in only two cases for castles of consequence, namely, Dudley and Belvoir. CHAPTER XII. OF THE EDWARDIAN OR CONCENTRIC CASTLES. Every castle, if more than a solitary tower or peel, and having more than a single line of defence, has more or less of a concentric character, but in most, even of the largest of the earlier castles, the secondary defences were of small extent and confined to works for the protection of the entrance, as at Richmond and Coningsborough, and such cannot, with any propriety, be called in a general sense concentric. At Richmond, for example, the original castle was an enclosure within a fortified wall of which the keep formed a part, a small barbican covering the entrance, and so of the purely Norman part of Corfe, of Coningsborough, of Brough, of Bridgnorth, and probably of the original Tower of London. None of these were originally concentric, nor can the term be correctly applied to the original castles of the early part of the reign of Henry III., nor even to some of those built by his son. White Castle, Grosmount, Cilgerran, and even Caernarvon and Conway, are mere enclosures, strengthened and fortified by mural towers and gatehouses upon a single line of wall. Salisbury was concentric by necessity, the earthworks leaving the builders no choice in the matter. The concentric arrangement has been supposed to have been introduced by Prince Edward from Syria. That so able a soldier, and so shrewd an observer, added to his knowledge of the military art by what he saw in Palestine is probable enough, but the system of defence for which his reign became celebrated was in truth introduced into England before the death of Henry and before Edward returned from the East. Caerphilly, one of the most complete examples of the concentric lines of defence, was constructed just before Henry’s death, and was the work, not of the sovereign but of a subject. Nevertheless, so great was Edward’s fame, that the system which, though he did not invent, he adopted, has been designated by his name, and the term Edwardian has been applied to that style of fortress, that took the place both of the round tower and of the walled enclosure, and carried forward the art of fortification from the Early English to the Decorated period of English architecture.