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Artillery castle at Upnor

A Scheduled Monument in Frindsbury Extra, Medway

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Latitude: 51.4069 / 51°24'24"N

Longitude: 0.5269 / 0°31'36"E

OS Eastings: 575842.292976

OS Northings: 170572.761611

OS Grid: TQ758705

Mapcode National: GBR PPH.N1Z

Mapcode Global: VHJLN.2WWV

Entry Name: Artillery castle at Upnor

Scheduled Date: 28 January 1960

Last Amended: 10 July 1996

Source: Historic England

Source ID: 1012980

English Heritage Legacy ID: 27007

County: Medway

Civil Parish: Frindsbury Extra

Traditional County: Kent

Lieutenancy Area (Ceremonial County): Kent

Church of England Parish: Frindsbury All Saints

Church of England Diocese: Rochester


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
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.

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

Source: Historic England

Reasons for Scheduling

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

Source: Historic England


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

Source: Historic England

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