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History of the Upnor Castle

Upnor Castle started to be built in 1559, and took five years to finish. The sheltered position of the River Medway, so close to London, was the main reason why it was used to build and repair warships, as well as being used as a mooring point, in the 16th century. The order to build Upnor Castle was given by Queen Elizabeth I and her Privy Council. After building a naval dockyard at Chatham, they realized that a fort needed to be built a short way downstream, in order to protect the anchorage, and fill a void in coastal defences. The fortifications were designed by Sir Richard Lee, while the site itself was supervised by Humphrey Locke and Richard Watts. By 1564, it housed twenty-three of the fleet’s largest ships.

During the British Civil War, in 1642, the Castle was surrendered to Parliament, however later during the Royalist rebellion it was briefly captured by the Royalists. The Fort was returned to Parliament following a visit by General Fairfax. The real test of the Castle’s defences came later, in 1667, during what is known as the Second Dutch War.

King Charles II of England had delayed peace negotiations, and during that year, had not launched the fleet due to financial problems. The Dutch fleet, under Lieutenant-Admiral Michiel de Ruyter, came up the River Medway towards Chatham unopposed, and burnt down the fort at Sheerness. Although a great metal chain had been slung across the river, between Gillingham and Ho Ness, a Dutch ship broke this line of defence, rendering it harmless. Many ships that were lying along the dockyard wall were burnt and destroyed, others were captured. After this disastrous loss, the remaining English ships retreated upriver to Upnor Castle, taking extra gunpowder for the expected battle. At this time, the Fort was under the command of Sir Edward Scott. A battery was formed to the north of the Castle, and another was constructed on the opposite bank of the river. The Dutch warships engaged Upnor Castle and the makeshift batteries.

Three English warships were burnt, many men killed and others wounded. Moreover, the dockyard was blocked by various ships that had been sunk by the English themselves, in order to prevent the Dutch from seizing them. This induced the Dutch to break off their attack, and sail back down the Medway with their prizes, leaving the English fleet in tattered defeat. Upnor Castle had failed to reach its target – it had proved ineffective under naval onslaught, mostly because at the time it was not well manned or well maintained. Despite the landward defences, Upnor Castle’s primary role had been to fire on enemy ships sailing up the river, not to repel direct attacks. It failed in its mission to halt the Dutch because of a fatal flaw in its design – the water bastion was star-shaped, which meant that only one side of it faced upriver. This means that there were not enough gun emplacements to fire effectively on a fleet approaching down the River Medway.

During the 17th century, the importance of Upnor Castle declined, and in 1668, it was converted from service as a military fortress into use as a naval ‘magazine’, that is, an ammunition storage structure. Hundreds of barrels of gunpowder were shipped here from Tower of London Wharf. In 1808, a purpose-built gunpowder magazine designed to hold 10,000 barrels was constructed downriver of the Castle, and another bigger one was built adjacent to it in 1856/7. More buildings were added throughout the years for the filling of bullet-shells and the storing of guncotton. Most of these were later demolished but the first magazine remains standing.

In 1827, Upnor Castle was converted to serve primarily as an Ordnance Laboratory, though gunpowder continued to be stored there until 1913. In 1891, the Castle was transferred from the Admiralty to the War Office, until 1945, when it was declared a museum owned by the English Heritage and run by the Medway Council.