upper storeys of the keep, the towers, the covered passageways and the gatehouse were all demolished, along with some of the buildings in the inner ward. The resulting rubble was used to backfill the outer ward, raising its height and effectively turning the inner ward into a dry moat. The inner curtain wall was reduced to one storey in height, and the outer curtain wall was refaced. An esplanade and wall-walk were built around the remaining outer walls, which supported at least eight gun emplacements. The circular keep was turned into a Martello tower, a type of Napoleonic artillery fortification. It was now only two storeys tall, although remaining original interior walls and doorways largely survived untouched. It was accessed on the first floor via an unusual sliding drawbridge, which was supported on rails and could retract into the floor, and the different storeys were linked by a spiral staircase. The ground floor of the keep included a brick-built magazine, and the roof, supported by a central pillar running up through the building, held a single, large gun emplacement. The north-east and north-west towers, now only one-storey tall, were covered with turf, turning the rear of the outer ward into a flat, grassed esplanade. The southern tower was reduced in height to two storeys, but remained in use as a gun platform. The covered corridors between the keep and the towers were now one-storey high as well, linking to the buried towers in the north-east and north-west bastions. The upper storeys of the gatehouse were rebuilt, although the ground floor remained in its 16th-century condition. The modified castle was completed by 1808, and held eight 24-pounder (11 kg) guns along the outer wall, a gun on the roof of the southern bastion, and another on top of the keep itself. The new castle could hold a garrison of 40 men. In 1859, the castle was re-equipped with heavier artillery, a combination of 32-pounder (15 kg) and 68-pounder (31 kg) guns. A new magazine was constructed, comprising a large, brick-built building divided into three rooms for storing gunpowder, specially designed to keep the powder dry. The exterior gun emplacements were also redesigned, reusing the 1806 foundations; the two surviving emplacements, in the north-east and north-west bastions, date from 1859. Coastal erosion remained a problem. By the middle of the century, the tides had reached the southern edge of the castle, and