Grain Fort was constructed in the 1860s to defend the mouth of the River Medway and Thames against the threat of French naval attack. It was designed to support both Grain Tower out at sea, built from 1848-55, and Garrison Point Fort at Sheerness. It was altered and upgraded during proceeding conflicts, including the First and Second World Wars, until it was decommissioned in 1956. After this, it was mostly demolished although remnants of the front of the fort can be seen today including it’s filled-in gun pits along the terreplein (upper surface) amongst a shrubbed coastal park and World War Two spigot mortar bases for use by the Home Guard. Underground, more substantial sections of the fort survive as two sets of subterranean tunnels, including the main magazine, caponiers, and ammunition lifts.
One of the two surviving underground tunnels contains a magazine chamber for storing munitions and explosives, as well as a lighting passage kept separate from the magazine by a staired passageway leading to an area in which lanterns would have been lit, closed off from the magazine by thick glass to prevent any explosive material from being ignited. Inside was an ammunition lift as well as a few furnishings such as original beds; all heavily decayed. It was entered via the remains of a caponier; a defensive protrusion into the ditch surrounding the fort. Also, two drawbridges still exist in the tunnel to protect it from a potential invader. Medieval types of defence such as this still had relevance in the 19th Century. Whilst some of the pulley mechanism and drawbridge pits survived, the actual bridges had long-since disappeared meaning we had to cross them via some very precarious wooden planks. The other tunnel was still impressive, but contained fewer items of interest. The tunnels were truly amazing to visit and their size and scale was impressive, especially considering that they lie under a public park unbeknownst to the thousands of visitors the park sees every week.
More detailed info about the tunnels can be found here at Subbrit
Sources & Image Credit: