 On Llanblethian Hill is the site of "Caer Dynnaf", a large Iron Age fort, whose walls and ditches can still be seen.Although no reliable accounts exist of life in Glamorgan in the first 150 years of Norman rule it is known the manor of Llanblethian existed as one of the twelve "member lordships", large areas of land that Glamorgan was divided up into by the Norman Lord Robert Fitzhamon.Most of these manors, specifically the hilly valley regions were held by subservient local Welsh rulers, but Llanblethian and its neighbor Talyfan were held by Norman feudatories, including Robert de Wintona, who built the Llanquian Castle.