Fort Darnet, like Fort Hoo was built on the recommendations of the 1859 Royal Commission on an island covering the inner navigable channel of the Medway, Kent. Originally designed for 2 tiers of guns mounted in a circle, with a boom strung between them, there were many problems with subsidence, and after extensive cost overruns the forts were completed in 1871 with 1 tier, and 11 guns, a mixture of 9" and 7" RMLs, and no boom. The forts were never used in anger, and were disarmed before WWI. In WWII the fort was used as observation posts, with platforms and pillboxes built on top. Currently the fort is in fair condition, and can be freely visited by boat, though the landing is muddy.