Durham Castle was ordered in 1072 as Norman rule struggled to secure northern England after conquest, rebellion, and the devastating Harrying of the North. Its position on a steep peninsula above the River Wear protected the town and the shrine of Saint Cuthbert while guarding routes toward Scotland. Earl Waltheof was tasked with construction, though he later rebelled and was executed. Early curtain walls, a motte, and the Norman Chapel established a fortress from which royal and ecclesiastical authority could be imposed on a region that had resisted William the Conqueror.

The bishops of Durham soon became rulers as well as churchmen. In return for defending the frontier, they exercised exceptional powers within the palatinate, including courts, taxation, military organization, and at times coinage. The castle was their principal urban residence. Bishop William de St-Calais took refuge there during the rebellion of 1088, while later bishops added halls, chapels, kitchens, and apartments. By the fourteenth century Bishop Antony Bek’s great hall expressed wealth and quasi-princely status, turning a Norman fortress into a palace for governance and hospitality.

Durham’s prince-bishops remained involved in warfare and diplomacy with Scotland, but Tudor monarchy reduced their independence. Bishop Cuthbert Tunstall remodeled the gatehouse and built a chapel and gallery suited to Renaissance court life. The Reformation placed him in repeated conflict with royal religious policy and stripped the bishopric of important secular privileges. During the seventeenth-century wars, Scottish armies occupied Durham. After the Battle of Dunbar in 1650, the castle served as a hospital for Scottish prisoners; archaeological discoveries near the site later revealed mass burials connected with their captivity.

The Restoration returned the bishops, and John Cosin rebuilt damaged rooms, created the Black Staircase, and reestablished the castle as a ceremonial palace. Yet the political power of the palatinate continued to decline. William Van Mildert, the final prince-bishop, supported the creation of Durham University in 1832. After his death, the castle was formally transferred to the university in 1837 and became University College. The keep was reconstructed for student rooms, beginning an unusual modern chapter in which medieval and early modern spaces remained in daily residential use.

Durham Castle continues to house students, meals, worship, teaching, and ceremonial events rather than functioning solely as a museum. Conservation must therefore protect fragile fabric while accommodating a living college. Together with Durham Cathedral, the castle was inscribed as a UNESCO World Heritage Site in 1986. Its buildings record nearly a thousand years of institutional change: conquest fortress, seat of prince-bishops, wartime occupation and hospital, and university residence. Few castles preserve so clearly the transition from military control to regional government, ecclesiastical magnificence, and modern education.