Llawaden Castle was originally an earth-and-timber ringwork, built circa 1115 on the frontier between Welsh and Norman/Flemish occupied regions, but was razed to the ground in 1193, and it was not until the Normans began to gain control in the region in the early thirteenth century that the site was refortified with a masonry curtain and several towers.
Bishop Bek (1280-93), seeking to develop the See of St. Davids, created the borough of Llawaden (NPRN 268099) and invested heavily in the region, building a hospital in 1287 (NPRN 32084). There is no evidence of work being carried out on the castle, however, until the episcopate of Adam de Houghton (1362-89). It is to this period that the majority of the visible remains date. Llawaden Castle was abandoned as a residence in the fifteenth century, but remained in administrative use, acting as a bishops prison, until the Reformation, following which it rapidly fell into decay.
The dried moat encircles an oval area roughly 55m across, upon which can be seen the ruins of a twin-towered gatehouse, a winged building which contained the great hall, kitchens and bishops? chamber, residential apartments, chapel and lodgings. The remains of two polygonal towers are well preserved, and the base of the original thirteenth century round tower is still in evidence.

Source: Turner, Rick. 2000. Lamphey Bishop's Palace, Llawaden Castle, Carswell Medieval House and Carew Cross: Cadw Guide (Revised Edition)

K Steele, RCAHMW, 10 November 2008