The Decline of Castles
Changes in society gradually led to the decline of the castle. Where the castle had once served an important defensive, administrative and residential role these functions were now being better served by other buildings. Nobles looked for more comfortable homes while forts manned by professional soldiers took over the defensive duties. Some castles remained a centre for local administration and many served as prisons long after they had ceased to serve a residential role. Some castles were turned into luxurious palaces, but this was expensive, and it was usually cheaper to construct a new home, often using building material from the old castle.
Corfe Castle, a Royalist stronghold during the Civil War, was once one of the strongest and most powerful castles in the country but was largely destroyed by Parliamentary forces at the end of the war to prevent any future threat against Parliament.
The fate of many castles was sealed by their role in the Civil War. Across the country, castles, whether derelict or still occupied, were refortified and used as bases for the opposing forces. Following their victory over the Royalists the Parliamentary forces adopted the policy of slighting - partially or totally demolishing castles to prevent their potential use in any future conflicts.
St Mawes Castle is a Tudor fort built as a base for canons to defend the entrance to Falmouth.
Changes in the way that battles were fought and advances in weaponry also contributed to the decline of castles. The design of the older castles meant they could not stand up to assault from cannon-fire, and this led to the development of new defensive structures. In the 16th and 17th centuries, forts were constructed that could withstand canon-fire while providing a base for their own batteries of guns. Forts, such as St Mawes Castle in Cornwall, were built by the state at strategic points, purely for the purpose of defence.
The last great fortifications to be built in Britain were initiated by Prime Minister Palmerston in the 1840s. Designed to protect the south coast from the threat of France, they were made obsolete by advances in artillery almost as fast as they were built. Good examples are Fort Brockhurst and Fort Nelson in Hampshire.