demolished during the period of the English Commonwealth in the 17th century when Oliver Cromwell's Parliamentary Commissioners sold it for £40 to a builder, John Warr of Westminster, who planned to quarry it for its stones. Very little work took place, however, and the Crown reacquired the castle in 1660. It was restored to the possession of the Pelham family, until in 1730 the Duke of Newcastle resigned it to Spencer Compton, 1st Earl of Wilmington. It was subsequently acquired by the House of Cavendish. In 1925 its last private owner, the 9th Duke of Devonshire, gave the castle to the state as a historic monument and it underwent repairs and some reconstruction under the supervision of the Ministry of Works. It acquired a fresh military significance in 1940 when Pevensey's exposed shoreline and flat hinterland became a possible target area for a German invasion after the fall of France. It was reoccupied by the military for the first time in over 400 years, with British and Canadian troops garrisoning it from May 1940, and Americans later. The towers of the inner bailey were converted into troop accommodation by lining the walls with bricks and laying wooden floors. New perimeter defences were constructed; machine-gun posts were built into the walls, disguised to look like part of the original structure, and an anti-tank blockhouse was built in the entrance of the Roman west gate. The main and postern gates of the inner bailey were blocked by concrete and brick walls, and anti-tank cubes were installed along the areas where the Roman curtain wall had collapsed. The main concern was that an invader could have captured the castle and used its interior as a strongpoint. It was intended that the new defensive measures at the castle would make it "100% tank-proof" and that an enemy would not be able to approach within of it. The United States Army Air Corps also used it as a radio direction centre from early 1944. In 1945 the castle was returned to civilian control. The blockhouse and obstructions were demolished but it was decided to leave the machine-gun posts in place to illustrate the most recent chapter in the castle's history. The castle is now managed by English Heritage and is open to the public. Archaeological investigations Pevensey Castle has been the subject of a number of excavations and archaeological investigations over the past 300 years.