On the Honddu above Brecknock was Castell Madoc, probably a Welsh fortress, and on the Llyfni between Brecknock and Hereford the Peel of Talgarth and the very remarkable cylindrical tower of Bronllys. The remains of the castle of Hay stand upon the Wye at the north-eastern angle of the county. It was built by Sir Philip Walwyn, destroyed by Henry III. in 1231, and probably rebuilt soon afterwards. A part of it is still standing. The town was walled and had three gates. Besides these were Scethrog, the tower of Sir Miles Pichard; Burghill, built by Sir Humphrey of that name; Langoed and some others, fortified houses rather than castles, and of which in most cases nothing remains but the moated mounds, only a few of which have been occupied by the Normans. Monmouthshire, though exposed to occasional inbreaks, was, in the eleventh century, and especially after Harold’s Welsh war of 1063, as completely a part of England as Hereford or the contiguous parts of Gloucester. Its western border was the Rhymny, but by much its more important part lay between two very deep and rapid rivers, the Wye and the Usk, and upon each were posted formidable castles; those of Monmouth and Chepstow upon the one river, and those of Newport, Usk, and Abergavenny upon the other. Chepstow is placed upon a cliff on the western or right bank of the river, evidently, like Newport, intended as a “tête du pont” to cover the passage of troops, the river not being there fordable. As the name imports, the settlement is of English origin, though its Domesday designation, Estrighoil, corrupted into Striguil, is Welsh. The castle is divided from the town by a deep ravine, and is altogether outside the wall, which was unusual. The keep, of Norman masonry, may be the work of William Fitz Osborne, Earl of Hereford, or at latest of Roger de Britolio, his son and successor. As early as in the reign of Henry I., Chepstow had come into the possession of the De Clares of the Strongbow line, often called Earls of Striguil. Its possession enabled the Mareschals, successors to the De Clares, to hold their earldom against Henry III. Monmouth Castle occupied the top of a promontory of rock between the Wye and the Monnow, and was long held by a line of border barons to whom it gave a name.