Artillery castle at Upnor


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:
Date of most recent amendment:


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The building or site itself may lie within the boundary of more than one authority.

Medway (Unitary Authority)
Frindsbury Extra
National Grid Reference:
TQ 75848 70581

Reasons for Designation

Artillery castles were constructed as strong stone defensive structures specifically to house heavy guns. Most date from the period of Henry VIII's maritime defence programme between 1539 and 1545, though the earliest and latest examples date from 1481 and 1561 respectively. They were usually sited to protect a harbour entrance, anchorage or similar feature. These monuments represent some of the earliest structures built exclusively for the new use of artillery in warfare and can be attributed to a relatively short time span in English history. Their architecture is specific in terms of date and function and represents an important aspect of the development of defensive structures generally. Although documentary sources suggest that 36 examples originally existed, all on the east, south and south east coasts of England, only 21 survive. All examples are considered to be of national importance.

The development and history of Upnor castle is well documented by surviving construction drawings, building accounts and contemporary records. It was the last artillery castle to be built in England and its design differs markedly from that of earlier examples. The castle survives well in the form of standing remains and earthworks, and the detailed interpretation of these has increased our knowledge of both the original form and strategic importance of the castle, and its subsequent remodellings and changing use over the years. Its close association with the naval dockyards at Chatham provides evidence for the importance of the Medway for naval defence from the Elizabethan period.


The monument includes an artillery castle situated on the north western bank of the River Medway. The castle survives in the form of standing buildings and ruined structures, Listed Grade I, and earthworks. It was built in two main phases, initially between 1559 and 1567 to a design by Sir Richard Lee, in order to provide increased protection for Queen Elizabeth I's warships, most of which were anchored when out of commission in the sheltered Medway estuary at the nearby, newly established dockyards at Chatham. The second phase of construction, dating to the years between 1599 and 1601, aimed mainly to improve the landward defences of the castle. The castle also shows signs of later remodelling and repair. The castle is constructed of ragstone faced with coursed ashlar blocks, along with some red brick. Much of the masonry was imported from earlier, derelict buildings demolished for the purpose at Rochester Castle, Aylesford and Bopley. Additional stone was transported from quarries at Bocton. Its defences are largely orientated towards the river and range around a north east to south west aligned, two-storeyed rectangular block measuring 41m by 21m. This originally provided accommodation for the garrison, and has a frontage which includes a central, polygonal bay containing a circular staircase, and circular turrets with garderobes, or latrines, projecting from either end. The facade is pierced by original doorways with four-centred heads at ground floor level and by bulls-eye and round headed windows with classical mouldings, inserted during the 18th century, on the first floor. Projecting out over the river from the main building is a low, triangular, open gun platform, known as the water-bastion, which originally housed most of the castle's heavy artillery, now represented by six 19th century guns mounted on their original wooden carriages. The water-bastion receives additional protection from a continually renewed, staked palisade, originally erected in 1600. To the north east and south west are two square, flanking towers linked to the main building by a crenellated curtain wall. These are fronted by semicircular stair turrets which incorporate splayed gun embrasures at first floor level. To the north west the main building is backed by a rectangular courtyard bounded by a stone built curtain wall topped with brick coping. This enclosing wall was largely rebuilt, after being allowed to fall into disrepair, during the 17th century, and is now around 1m thick and c.4m high. Running along the inside of the curtain wall are the brick foundations of now ruined, narrow lean-to buildings, also dating to the 17th century, which were originally used for storage. In the north western corner is a sallyport, with a later inserted oven beside it. The castle's well is situated within the north western quarter of the courtyard. The castle buildings are entered by way of a centrally positioned, four-storeyed gatehouse in the north western side of the curtain wall. This has a central, round-headed gateway, above which is an inserted, late 18th century clock, leading into a wide entrance passage. Flanking the gateway on its inner side are two tall, rectangular corner towers. Gun embrasures pierce the walls of the gatehouse and provide further protection for the entrance. The gatehouse was remodelled during the early 1650's, and heightened in brick after a fire caused substantial damage in 1653. It is now capped by an early 19th century wooden bellcote and modern flagpole. The castle is enclosed on the landward side by a substantial dry ditch, originally 9.8m wide and 5.5m deep, which has become partially infilled over the years. This was originally spanned by a drawbridge, although this no longer survives. By 1588, the year of the Spanish Armada, the castle's garrison included six gunners and a master gunner, and in 1603 it is recorded as housing 19 heavy guns. The castle did not see action until June 1667 when, during the Second Dutch War, an enemy navy squadron under de Ruyter launched a successful surprise attack on the Thames and Medway defences. The squadron broke through the chain boom-defence which had been positioned across the river between Hoo Ness and Gillingham and threatened Chatham dockyard. Much English shipping was destroyed before a hastily organised defence at Upnor stalled the Dutch attack. This episode provoked a radical revision of south eastern coastal defences and the building of new forts along the Medway. These reduced the strategic importance of the by now old fashioned castle and in 1668 it was converted into a magazine and naval storage depot. The depot buildings gradually extended into the area to the north east of the monument which is still used by the Ministry of Defence, disturbing and overlying earlier gun emplacements associated with the castle. The earthwork remains of these are thought to be represented within the monument by a broad bank around 14m wide running parallel with the river from the ground immediately to the north east of the castle towards the adjoining naval depot to the north east. During the 18th century, the castle's accommodation was extended by the construction of a new barracks block and associated storage buildings on land immediately to the south west of the monument. The castle and its depot continued to supply munitions to the navy until 1827, when it was fitted out as an ordnance laboratory. In 1891 responsibilty for the administration of the castle was transferred from the War Office to the Admiralty, and the newly created Naval Armament Supply Department began to use it, amongst other things, as a proofyard. The castle served as part of the Magazine Establishment during World War II, and in 1941 was partially damaged by two bombs which fell in the garden of nearby Upnor House. After 1945 the castle went out of military use and was opened to the public. Upnor Castle continues to form part of the Crown Estate and is now in the care of the Secretary of State. All modern signs, fixtures, fittings and the modern surfaces of all paths and tracks are excluded from the scheduling, although the ground beneath these features is included.

MAP EXTRACT The site of the monument is shown on the attached map extract.


The contents of this record have been generated from a legacy data system.

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Books and journals
Saunders, A D, Upnor Castle, (1967)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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