Coordinates: 51°24′12″N 00°34′53″E / 51.40333°N 0.58139°E / 51.40333; 0.58139
Fort Hoo, like Fort Darnet was built on the recommendations of the 1859 Royal Commission on an island covering the inner navigable channel of the River Medway, Kent.History
Originally designed for two tiers of guns mounted in a circle, with a boom strung between Fort Hoo and Fort Darnet, there were many problems with subsidence, and after extensive cost overruns the forts were completed in 1871 with a single tier of eleven 9-inch rifled muzzle-loading guns, and no boom.
The forts were disarmed before the First World War. In the Second World War, the fort was used as observation posts, with platforms and pillboxes built on top. The fort is still in fair condition, however it is a Scheduled Monument owned by the Ministry of Defence and landing is not officially permitted.