Upnor Castle is an artillery fort located in the village of Upnor in Kent. Constructed between 1559 – 1567, it was constructed to a design by Sir Richard Lee to defend the Royal Navy dockyard at Chatham and ships anchored in the Medway. The castle was constructed on the orders of Elizabeth I (1558 – 1603) and consisted of a main block, water bastion and river frontage.
In 1599 – 1601, the castle was remodelled. Two riverside towers were rebuilt, a gatehouse, moat and curtain wall were added. The castle is constructed of ragstone faced with course ashlar blocks. Some red bricks were also used.
In June 1667, a Dutch squadron under the command of Michiel de Ruyter mounted a raid on the Medway, capturing two ships and burning others at anchor at Chatham. This defeat, was one of the worst in Royal Navy history and showed how inadequate the Medway defences were, including Upnor Castle. Though it should be noted that Upnor Castle had been neglected of investment, but acquitted itself better than some of the other Medway defences.
After the Dutch attack, the castle was retired from service as new and more advanced forts were built to protect the dockyard. Instead the castle was was used as a store and magazine. Works to the castle to make it fit for this purpose were undertaken, including the main building of the castle which had to be heightened and its floors reinforced.
In 1827, the castle ceased being used as a store and magazine, instead it was used as a ordnance laboratory. Later, in 1891, the castle came under the control of the Admiralty, ending the relationship where the Admiralty had managed the site and the War Office had funded it.
After the First World War (1914 – 1918), the castle became a Royal Naval armaments depot. During this time, weapons and explosives were tested at the castle. From the 1920s onward, the castle was a museum, though during the Second World War (1939 – 1945) the castle was still in use as part of the Magazine Establishment, with the castle being bombed in 1941.
After the war in 1945, the castle was opened to the public as a departmental museum by the Admiralty. The castle was restored at this time.
Today, the castle is managed by Medway Council and is open to the public.