Waterlogged, vandalised and forgotten, Cliffe Fort on the Hoo Peninsula just west of the small village of Cliffe, is another Victorian fort that never saw active service. Built in the 1860s as an artillery fort with large calibre guns to protect the Thames estuary, it was decommissioned in 1927 but finally saw 'action' during WWII as an anti-aircraft battery.
Not accessible to the public due to its private ownership and decaying condition, the fort sits on the Saxon Shore Way and makes for an interesting explore. Nearby is the remaining slipway for the Brennan Torpedo, claimed to be the first guided missile, patented in the 1870s. I didn't realise torpedos were that old.
There are plenty of nice walks in the area. The Saxon Shore Way from Cliffe to Gravesend is a particularly nice stretch. You'll need OS Explorer 163 Gravesend and Rochester.