Reported to be the oldest secular stone building in Wales, Chepstow – or Striguil as it was once known – lies on a cliff face high above the magnificent Wye river. It is a deceptively large, long and narrow castle that uses the geography of the landscape to its advantage.
In 1189, Chepstow Castle was inherited by William Marshal through his marriage to Isabel de Clare, daughter of Richard (Strongbow) de Clare. With his considerable experience in military architecture learned from his many years in France, Marshal set about modernising and strengthening the castle. He rebuilt the east curtain wall, with two round towers projecting outwards, in order to protect this vulnerable side. The arrow-slits were designed to give covering fire to the ground in front of the towers and was one of the earliest examples of the new defensive mode which was to become characteristic of the medieval castle. He also improved the defences of the lower bailey, having an impressive and cutting edge twin towered gatehouse built. This gatehouse had a small barbican, double portcullis, murder hole, arrow slit and heavy iron plated, oak doors.
The original castle doors are still on display at Chepstow Castle and are the oldest castle doors in Europe, dating from no later than 1190. After Marshal had inherited Chepstow Castle, the significant and extensive alterations he made were revolutionary and marked the transition from square towers to the form that was adopted by castle builders in the 13th century. He transformed it from a Norman great hall into the impenetrable fortress it remains to this day.
After William’s death in 1219, his sons continued to enlarge Chepstow's defences and improved the internal accommodation. They added a heavily defended barbican at the rear of the castle. They were given assistance by Henry III who had visited the castle prior to William's death and his donation helped with the remodelling of the Great Tower which had remained largely unchanged since it was originally constructed in the late 11th century.