Chepstow Castle was begun in 1067, only a year after the Norman Conquest of England. William FitzOsbern, one of William the Conqueror’s closest allies, established the fortress above the River Wye to control an important crossing and to support expansion into Wales. The Great Tower was built in stone from the outset, an exceptional investment at a time when many Norman castles were earth and timber. Roman masonry reused in its walls linked the new lordship to older traditions of imperial authority while the cliff and river gave the site formidable natural defenses.

Chepstow passed through royal and aristocratic hands before becoming a principal residence of William Marshal, celebrated as a knight, regent, and earl of Pembroke. From the 1190s, Marshal and his sons enlarged the castle with new defenses and domestic ranges suited to a great household. The main gate and other works incorporated ideas encountered in contemporary warfare. Remarkably, timber doors dated to this period survived at the entrance for centuries. The Marshal family made Chepstow both a military base on the Welsh March and an expression of international aristocratic status.

In the later thirteenth century, Roger Bigod, earl of Norfolk, transformed the upper parts of the complex. He added comfortable apartments, service buildings, and the tower later associated with Henry Marten, along with stronger walls and gateways. By then Edward I’s conquest had reduced the castle’s frontier role, yet Chepstow remained an administrative center and prestigious residence. Its layout records this transition: severe defensive works stand beside halls, chambers, kitchens, and river access designed for the movement and display of a wealthy lordly household.

The English Civil War returned Chepstow to military use. Royalists held it during the first conflict before Parliamentary forces captured it in 1645. A renewed Royalist rising in 1648 brought a second siege. Parliamentary guns breached the defenses, and the commander Sir Nicholas Kemeys was killed when the castle fell. Afterward, parts of the fortifications were damaged to prevent further resistance. The castle also served as a prison; the republican Henry Marten, who had signed Charles I’s death warrant, was confined there from 1668 until his death in 1680.

By the eighteenth century, Chepstow was no longer a working fortress, but its cliffside ruins became an important destination for travelers following the picturesque Wye Tour. Artists and writers treated the castle as a place where architecture, landscape, and reflections on the past could be combined. Government care and systematic conservation in the modern era protected its masonry and documented the changing uses of its buildings. Chepstow now offers one of Britain’s clearest architectural narratives of conquest, Marcher lordship, aristocratic residence, civil-war stronghold, state prison, and romantic ruin.