Revolt in Wales - Herbert to Llanstephan, I remember it from Kingmaker, well I managed to get to Llansteffan while on holiday. It's free entry, which is quite a surprise for a sizable castle, but you do have to negotiate the narrow country roads, especially along the route Google maps sent me. The direct route from Carmarthen is OK.
Park at the beach car park and after a ten minute walk uphill you reach the castle, the gatehouse is the largest structure. The view upriver towards Carmarthen
The gatehouse of the inner bailey
The view south from the top of the great gatehouse An interpretation of how it might have looked