Slough Fort is a small artillery fort that was built at Allhallows-on-Sea in the north of the Hoo Peninsula in Kent. Constructed in 1867, the D-shaped fort was intended to guard a vulnerable stretch of the River Thames against possible enemy landings during a period of tension with France. Its seven casemates initially accommodated rifled breech loading guns, which were replaced by the turn of the century by more powerful breech-loaders on disappearing carriages, mounted in concrete wing batteries on either side of the fort. It was likely one of the smallest of the forts constructed as a result of the 1860s invasion scare.