The Normans in Normandy, towards the middle of the eleventh century, and in England a little later, and onwards into the reign of Henry II., commonly replaced these defences by more substantial walls of masonry, which, being of great thickness and solidity, have often remained to the present day, though more frequently they were removed in the reigns of the earlier Edwards, to be replaced by structures of more scientific though less solid design, affording more accommodation within the _enceinte_. At Hawarden, the course of action seems to have been different. Here are no traces of Norman work or of the Norman style, and though the keep is unusually substantial, it bears evidence of being the work of one period, and that the close of the reign of Henry III. or early in that of Edward, his Welsh-compelling son. If this be so, it must be concluded that the Norman barons, who were known to have held Hawarden in the twelfth century, were content to allow its defences to be formed of timber, as any masonry constructed by them would scarcely so soon have needed to be removed. The _Keep_ (A in the plan) very nearly covers the top of the mound. It is circular, 61 feet across at the base, and originally about 40 feet high. The base gathers inwards to a height of 5 feet, where the cylinder is 59 feet across, and from hence to the summit it further diminishes to 57 feet. The interior is vertical, and 31 feet diameter throughout; hence the wall, which is 15 feet thick at the base, and 14 feet a little above it, is 13 feet at the level of the rampart walk; dimensions of unusual solidity even at the Norman period and very rare in England under Henry III. or the Edwards. The exterior is very plain, having neither cordon, string-course, nor window labels. A little above the ground is a double course of large ashlar blocks of a light yellow sandstone, tying the work firmly together, and higher up are other bonding courses of a less substantial character. The ordinary material is a bluish stone laid as rubble work, with the spaces and joints neatly filled up with spawls and fragments. The battlements have been replaced by a modern wall, but the junction, at the rampart walk, may be readily detected.