The science of medieval warfare and the design of castle architecture developed side by side until the latter reached its highest degree of sophistication in the almost impregnable concentric castle, exemplified in the royal castle at Dover, known as the “key of England,” the first castle of its kind in western Europe. On a clear day the French coast, 21 miles (37 kilometers) across the English Channel, can be seen from the ramparts above the famous white cliffs of Dover, Europe’s historical gateway to Britain.
In 55 b.c. Julius Caesar landed his reconnaissance force nearby, and following a full-scale invasion in a.d. 43, the Romans built a walled town, Dubris (from which Dover is derived). They built an 80-foot-high (25-meter) flint pharos (lighthouse) on the nearby 375-foot (114-meter) Castle Hill, the site of an Iron Age earthworks that had existed long before. It was inevitable that the commanding position would continue to be used for defense. In the fifth century the Angles and Saxons came in the wake of the Roman withdrawal and founded a fortified town on the hill, employing the ancient defenses. Once Christianized, they built the church of St. Mary-in-Castro (St. Mary in the Fortress) as a chapel for the castle garrison and adapted the Roman lighthouse as part of its bell tower.
William I (the Conqueror) also recognized the strategic value of Dover. He instructed his half brother,
Odo of Bayeux, should the Norman invasion succeed, to land there with building materials for a castle. It took just eight days in 1066 to construct the fortress—probably a motte and bailey—within the Anglo-Saxon earthworks. Nothing of it remains. The motte was an earth mound crowned with a wooden keep and guarded by a wooden palisade; the bailey was a defensible area, also with a palisade and connected to the motte by a bridge. All was surrounded by a ditch. The earliest stone castles were organized in the same way.
Castles multiplied in Britain after the Conquest, responding to the internal tensions created by the feudal system. Dover continued to be strategically important in an international context, a “royal castle” that was not for a feudal baron but for the defense of the realm. Its evolution into a finely tuned concentric castle was a response to changes in medieval military technology and the science of war. Little is known of its earlier defensive works, but extensive rebuilding was undertaken after 1168. Most work was carried out in the 1180s under the supervision of King Henry II’s chief architect, a master mason known only as Maurice. Richard I (the Lionhearted) almost completed it in 1189–1190, and his brother John extended the outer curtain wall at the north side so that the outer bailey had been enlarged to include most of the hilltop. The “completed” castle dates from about 1200. Repairs and extensions were necessary after a siege by rebel barons and their French allies in 1216, during which, despite the collapse of the east tower, it was successfully defended by a force of only 140 knights and men-at-arms. By 1256 Dover Castle reached its maximum strength and size, its outer walls then extending to the cliff’s edge.
Dover Castle, Kent, England; architect(s) unknown, ca. 1168–1200. View showing concentric curtain walls and keep.
Concentric castles comprised a carefully designed keep that was the last line of defense, surrounded by a curtain wall that enclosed a large bailey. Sometimes there was a second, slightly lower curtain wall
(as at Dover) or even a third. Most functions were served by buildings in the bailey. Dover’s daunting keep—the largest in England—was almost 100 feet (30 meters) square and 95 feet (29 meters) high; in places its walls were 21 feet (6.5 meters) thick. It was defended by an inner curtain wall with fourteen projecting “mural towers”—the first in England—which allowed archers to shoot toward any point at the base. The outer curtain wall at Dover was nearly 1 mile (1.6 kilometers) in circumference, with 20 similar towers. Each wall was interrupted only by fortified gatehouses with barbicans. When gunpowder was introduced into the country in the fourteenth century, cannon were developed that could shoot missiles 3 miles (5 kilometers). Given the thickness of its walls, that was of little consequence to Dover Castle. It has been involved in almost every conflict since the Middle Ages. Small wonder it has been called England’s greatest castle.
Changes to artillery were not the main reason for the demise of castles; rather, the feudal system gave place to centralized government and the power of the monarch. In Tudor times, the design of castles was to alter dramatically. As a royal castle, with an eye on the Spanish, Dover was heavily fortified with cannon in the reign of Elizabeth I. It continued to function well beyond that: it was “modernized” during the Napoleonic Wars. Caves were excavated to hide troops waiting in ambush should the French invade. The towers were truncated—some say vandalized—to serve as gun platforms. The caves were again used as headquarters of the Dover Patrol in World War I and as bomb shelters and a hospital in World War II. The castle remained in the hands of the British army until 1958; five years later it was put in the custody of the Department of the Environment (now English Heritage) as a national monument. Conservation work continues.