Chepstow Castle (Welsh: Cas-gwent), located in Chepstow, Monmouthshire in Wales, on top of cliffs overlooking the River Wye, is the oldest surviving stone fortification in Britain. It was built under the instruction of the Norman Lord William fitzOsbern, soon made Earl of Hereford, from 1067, and was the southernmost of a chain of castles built along the English-Welsh border in the Welsh Marches. 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. However, it was 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, derived from the Welsh word ystraigl meaning river bend. FitzOsbern also founded a priory nearby, and the associated market town and port of Chepstow developed over the next few centuries. The castle and the associated Marcher lordship were generally known as Striguil until the late 14th century, and as Chepstow thereafter. Further fortifications were added by William Marshal, Earl of Pembroke, starting in the 1190s. The wood in the doors of the gatehouse has been dated by dendrochronology to the period 1159-89. Marshal extended and modernised the castle, drawing on his knowledge of warfare gained in France and the Crusades. He built the present main gatehouse, strengthened the defences of the Middle Bailey with round towers, and, before his death in 1219, may also have rebuilt the Upper Bailey defences. Further work to expand the Great Tower was undertaken for William Marshal’s sons William, Rich...