1867 continues in use, and is protected as a grade II listed building. The spit and the adjoining coastline is protected as an SSSI. The spit is subject to coastal erosion which has gradually pushed the spit towards the shore, a process which has eaten away at the remnants of the 1852 west wing battery and barracks, and has exposed the foundations of the later fortress on occasions. This erosion has increased significantly since the 1940s, due to the construction of groyne barriers at nearby Bournemouth and Christchurch which prevented the natural renewing of the spit with pebbles washed from local cliffs. Government efforts began in the 1960s to try to stabilise the spit in its current position, both to protect the castle and neighbouring towns, with over of gravel being laid down in the 1990s, and is continuing in the 21st century. Erosion caused fresh damage to the eastern end of the castle in early 2013, leading to renewed concerns. In January 2021, local media reported that the castle was in urgent need of repairs due to coastal erosion and the wall of the eastern wing partially collapsed on 26 February 2021. Efforts to repair the damaged wall commenced the following month, using shingle and granite to stabilise the section of the wall still intact and build a protective revetment, which was completed in June of that year. English Heritage reported that the full repair effort would take 'many months' to complete. In October 2021, the castle and lighthouse together were among 142 sites across England to receive part of a £35-million grant from the government's Culture Recovery Fund. In September 2022, it was one of six English castles included in a fundraising campaign by English Heritage to mitigate risks of destruction due to worsening coastal erosion. They hope to gather enough funds to repair and strengthen the sea walls around the castle. Architecture Central castle The central castle was originally constructed in the 16th century but heavily redeveloped in the early and middle years of the 19th century. It comprises a central tower with three bastions to its north-west, north-east and south, approximately across. A curtain wall with gun positions originally linked the three bastions, but this was substantially altered with the addition of walls and chambers to produce a deeper structure. The central castle forms the entrance to the rest of the fortification and is accessed through