The first castle at New Radnor may have been built by William Fitz Osbern earl of Hereford. Certainly he held the land by the time of his death in 1071 and the layout of the powerful castle suggests that it was built by a man of great influence. Soon after 1086 New Radnor was granted to Philip de Braose. It may have been at this time that ten minor castles were built nearby to strengthen the Norman hold on the district.