Details

This monument includes the earthwork, rock cut and some of the earth covered
parts of a Royal Commission fort known as Crownhill Fort, built between 1863
and 1872 as part of a series of defences which protected the city of Plymouth
and Devonport Dockyard from attack by land. Crownhill Fort was designed by
Captain EF Du Cane as the principal and largest fort of the defensive line,
and was set on a gently sloping hilltop 400m in advance of the main defensive
lines. For this reason, its defences entirely encircle the site, which sits on
the watershed between valleys running to the east and west, and also commands
the main road into Plymouth from the north. The fort is as outstanding example
of the later period Royal Commission fortifications and is the only one of
Plymouth's such forts to be actively preserved and opened to the public.
Crownhill Fort has an irregular septagonal plan and is accessed from the south
via a single storey stone gatehouse with brick vaulted ceilings and bomb proof
earth coverings. A Norman style granite outer arch, originally fronted by a
drawbridge, gives access to a tunnel through the gatehouse, which could be
defended as a keep with a second gate facing into the fort. Beyond the
gatehouse, the access road passes through an open well with stairs accessing
the rampart, before passing beneath the officers' quarters building and
curving to the west up a sloping ramp onto a large level semicircular parade
ground. Stone buildings of the 1870s-1890s surround this, some free
standing, but most consisting of vaulted structures with bomb proof earth
coverings. A single storey vaulted and earth covered range on the south side
of the fort contained the officers' quarters. On the north side a similar,
but two storied building contained the soldiers' barracks, with a vaulted and
earth covered three bay magazine to its west. To the east of the barracks, a
single storey cookhouse has a new roof of cast concrete construction. Other
buildings to the east and west are free standing, with two long field gun
sheds flanking the entrance to the south.
A heavy earthen rampart measuring from 20m to 30m wide surrounds the fort,
rising 8m from the interior. An intermittent firing step for infantry near
its crest is interspersed with 16 gun positions of varying dates, mostly
along the east and west sides of the ramparts, with a few along the north
side. An open terreplain, possibly for use by moveable field guns but more
likely for the assembly of infantry who would have manned the firing steps
on the southern rampart, runs along the rear of the southern rampart. The
fort was originally designed to contain 32 guns, including two sets of three
13 inch mortars in earthen pits on the west side of the fort, while four
single and one double stone and brick built Haxo casemates with bomb proof
earth roofs, which were finally armed in the 1880's with 7 inch Armstrong
breech loading guns on traversing carriages which defended the south west,
south east and eastern sides. The Haxo casemates were served by both
overground expense magazines with bomb proof earth coverings, and vaulted
underground magazines serving the casemates directly via hoists. These guns
were supplemented in the 1870s and 1880s by open concrete emplacements
containing three 64 pounder rifled muzzle loading guns; four Armstrong 7
inch guns mounted en barbette and two Moncrieff counterweight disappearing
carriages mounting Armstrong 7 inch breech loading guns, located on the north
west and north east angles. The guns mounted en barbette fired over low
concrete parapets, while the Moncrieffs lay inside high walled semicircular
emplacements. Ammunition recesses are cut into the rear of the rampart
between the open air gun positions. Similar ammunition recesses are provided
within the Haxo casemates.
The outer face of the earth ramparts slopes gently at first, then drops
steeply down to the top of a stone wall of dressed limestone and slate rubble
which falls 9m into a rock cut ditch, measuring 7m wide at the top. The ditch
sides batter in to a width of 5m at the flat bottom of the ditch. An open
chemin des rondes, vaulted on the two northern faces of the fort to form
covered rifle galleries, runs immediately inside the stone wall, with regular
musket loops positioned to give a wide field of fire over a glacis outside
the fort which falls away at an angle of 20 degrees until it strikes natural
slopes. The glacis is therefore of variable width, measuring 250m from the
outer edge of the ditch on the north west side, to 30m at the south east.
The angles of the fort are defended by three storied stone faced demicaponiers
with solid vaulted ceilings and bomb proof earth coverings. Each of these has
musket loops on the upper and lower floors, and paired gun loops on the
intermediate floors for 32 pounder smooth bore breech loading guns. Additional
musket loops on three floors were provided in the re-entrant angles of each
demicaponier, to cover the dead ground in front. All of these also contained
sally ports at the intermediate level to allow infantry to enter the ditch.
There are three demicaponiers on the east side and two on the west, those on
the east facing clockwise and those on the west facing anticlockwise. The
north angle of the fort has a trapezoidal full caponier located in a
semicircular ditched projection from the ramparts. This contained two sets of
the armaments found in the single caponiers, with additional musket loops and
with a fifth gun position on the north side. This fired directly into a
unique countermining gallery, served by two flights of stone steps leading
down from the covered way on the outer side of the ditch. The gallery passes
beneath the glacis and connects with the covered channels of Drake's and
Devonport Leats, which curve around the hill on which the fort lies. Between
the full caponier and the countermining gallery, the ditch widens to
accommodate a single storey miniature caponier projecting onto the ditch floor
This is rectangular, constructed of limestone ashlar with a solid stone hipped
roof and three musket loops on either side, covering the outer angles of the
full caponier. On the west side of the fort, the earth rampart angles back to
form two triangular spaces behind the western caponiers. Sunken mortar pits
here are accessed by tunnels beneath the ramparts from the fort interior and
chemins des rondes and were each intended to contain three mortars. Outside
the fort, a covered way for infantry runs along the outer edge of the ditch,
with an earthwork firing step for rifle fire across the glacis.
A number of features of World War I and II survive at the fort. Several
gunports in the caponiers were infilled with brick to allow the mounting of
machine guns to cover the ditches, while brick partitions in Drake's and
Devonport leats assisted in the defence of these parts with machine guns.
Several slit trenches were cut into the gently sloping outer face of the
rampart and were accessed from the terreplain behind. These trenches vary in
plan, but mostly run parallel to the ramparts with a central access to the
rear. They are now lined with corrugated iron, fixed in place with angle iron
posts, but were probably originally lined with timber. A number of foxholes of
the same construction were placed on the firing step along the covered way
outside the ditch. The drawbridge to the gatehouse was removed and replaced by
an earth ramp, its sides sloping gently into the ditch on either side.
Vehicles and equipment were stored here prior to the D Day Landings in 1944.
The covered parts of the leats were used as an air raid shelter for Water Boar
staff at the nearby water works.
A set of 1880s metal fence posts flanking the entrance cutting are included
within the scheduling, as are path surfacings on the ramparts and the floors
of the gun emplacements.
All free standing buildings, walls and road surfacings, all fence posts (apart
from the 1880s metal fence posts flanking the entrance) and the originally
earth covered buildings which have since had their earth coverings replaced
(which include the officers' and soldiers' quarters) are excluded from the
scheduling although the ground beneath these features is included. The
buildings which remain earth covered are included within the scheduling.

MAP EXTRACT
The site of the monument is shown on the attached map extract.
It includes a 2 metre boundary around the archaeological features,
considered to be essential for the monument's support and preservation.

Source: Historic England

Reasons for Scheduling

The Royal Commission fortifications are a group of related sites established
in response to the 1859 Royal Commission report on the defence of the United
Kingdom. This had been set up following an invasion scare caused by the
strengthening of the French Navy.
These fortifications represented the largest maritime defence programme since
the initiative of Henry VIII in 1539-40. The programme built upon the
defensive works already begun at Plymouth and elsewhere and recommended the
improvement of existing fortifications as well as the construction of new
ones.
There were eventually some 70 forts and batteries in England which were due
wholly or in part to the Royal Commission. These constitute a well defined
group with common design characteristics, armament and defensive provisions.
Whether reused or not during the 20th century, they are the most visible core
of Britain's coastal defence systems and are known colloquially as
`Palmerston's follies'. All examples are considered of national importance.

Despite slight damage to its glacis, and late 20th century refurbishment, the
Royal Commission Fort at Crownhill Fort is an outstanding example of its class
and is accessible to the public. Its earth ramparts, walls and ditch, and
outer glacis contain information about the fort's construction and use, while
the gun emplacements and associated service buildings which lie upon and
within the ramparts will contribute to an informed understanding of the site's
development. The survival of numerous slit trenches and foxholes of World War
II date provide evidence of the fort's later history.

Source: Historic England

Sources

Books and journals
Pye, A, Woodward, F, The Historic Defences of Plymouth, (1996), 175-178
Pye, A, Woodward, F, The Historic Defences of Plymouth, (1996), 175-178

Source: Historic England