the construction of a breakwater, and new forts were built on the Verne heights and the sea front to protect it, although the structure of the old castle itself was left untouched by the growing complex of forts. Charles died in 1869 and, amid ongoing invasion fears, the War Office took over the castle again for use as accommodation for commissioned officers, including as a house for the adjutant of the Verne Citadel. 20th–21st centuries In the early years of the 20th century, the War Office and the Office of Works held discussions on how to manage the castle. In 1908, Portland was placed onto what was known as the Schedule C list, which meant that the Army would continue to use and manage the historic property, but with input on repairs from the Office of Works. With the outbreak of the First World War in 1914, Portland Harbour became an important naval base and the castle was used an ordnance store. The castle became a military residence again in the interwar years, and during the Second World War it was used for accommodation and offices by British and US soldiers, with part of the castle used once again for storing ordnance. A concrete pillbox, since demolished, was constructed alongside the castle early on in the war. After the conflict, Portland Castle was transferred to the Ministry of Works in 1949 and opened to the public in 1955. The Ministry decided to present the interior as it might have looked in the 16th century and removed most of the 19th- and 20th-century additions and changes. The Captain's House and the adjacent gardens were used by the neighbouring HMS Osprey helicopter base until 1999, but with the facility's closure, this part of the fort was also opened to visitors, the house being turned into a visitor facility. In the 21st century the castle is operated by English Heritage as a tourist attraction, receiving 22,207 visitors in 2010. The main castle is protected under UK law as a Grade I listed building, and the Captain's House as a Grade II* building. Architecture The heart of the castle is the keep, across, comprising a central tower with two wings on either side and a gun battery to the front, together forming an unusual, fan-shaped design over-looking the sea. This is surrounded by a walled courtyard, approximately , with two gun platforms on either