Horse Sand Fort is situated in the Solent, between Southsea and the Isle of Wight, and is one of three similar sea forts constructed between 1865 and 1880 to head off the threat of seaborne invasion from France. The reputed original construction cost was £425,000! Extending to 9,197 sq.m. (99,000 sq.ft), the original fort was constructed over four levels, the middle two of which housed some 45 cannon, with further armaments on the roof. An inner courtyard housed accommodation and a well. In the Second World War additional structures were added to the upper storey, including look-out posts and anti-aircraft guns which were used to protect the nearby Portsmouth Dockyard. The nearby sister forts, No Mans and the smaller Spitbank, have both enjoyed a new lease of life in recent years with multi-million pound conversion into hotel and wedding/weekend retreat locations, but this one is still in much the same condition as it was when it was surplus to MOD requirements in the 1960s. A Planning Consent has previously been obtained for conversion to form 14 residential apartments, though this was not implemented.