Chepstow Castle.

“The speed with which William the Conqueror committed to the creation of a castle at Chepstow is testament to its strategic importance. There is no evidence for a settlement there of any size before the Norman invasion of Wales, although it is possible that the castle site itself may have previously been a prehistoric or early medieval stronghold. The site overlooked an important crossing point on the River Wye, a major artery of communications inland to Monmouth and Hereford. At the time, the Welsh kingdoms in the area were independent of the English Crown and the castle in Chepstow would also have helped suppress the Welsh from attacking Gloucestershire along the Severn shore towards Gloucester. However, recent analysis suggests that the rulers of Gwent, who had recently fought against King Harold, may initially have been on good terms with the Normans.”