Newcastle Castle was initially constructed as a ringwork 1106 by William de Londres, one of the legendary Twelve Knights of Glamorgan, as part of the Norman invasion of Wales. William de Londres was a knight loyal to the Norman baron Robert Fitzhamon and the Newcastle defences marked the most western extent of Fitzhamon's lordship. It is one of three castles built by the Normans in the area at the time, the others being Coity Castle and Ogmore Castle.