 During the late 11th century , the Norman lord , Robert Fitzhamon entered Morgannwg in an attempt to gain control of the area , building many earth and timber castles in the lowlands . In the early 12th century the Norman expansion continued with castles being founded around Neath , Kenfig and Coity , while within the same period Bishop Urban established the Diocese of Llandaff under which Glynrhondda belonged to the large parish of Llantrisant . 
