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Late 19th-early 20th century Steval Battery on The Garrison, St Mary's

A Scheduled Monument in St. Mary's, Isles of Scilly

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Latitude: 49.9125 / 49°54'44"N

Longitude: -6.3238 / 6°19'25"W

OS Eastings: 89703.390187

OS Northings: 10329.843351

OS Grid: SV897103

Mapcode National: GBR BXSX.D6P

Mapcode Global: VGYC4.BGRF

Entry Name: Late 19th-early 20th century Steval Battery on The Garrison, St Mary's

Scheduled Date: 1 August 1996

Source: Historic England

Source ID: 1014784

English Heritage Legacy ID: 15437

County: Isles of Scilly

Civil Parish: St. Mary's

Built-Up Area: Hugh town

Traditional County: Cornwall

Lieutenancy Area (Ceremonial County): Cornwall

Church of England Parish: Isles of Scilly

Church of England Diocese: Truro


The monument includes a large gun battery situated at the western edge of the
summit plateau of The Garrison, the south western promontory of St Mary's in
the Isles of Scilly. The battery is one of two complementary gun batteries
with a barracks/caretakers quarters between them, built on The Garrison
between 1898 and 1901, and forming part of a defensive system designed to
protect a naval signalling and re-fuelling station then being established on
the Isles of Scilly. The defences were initially operational until 1906 but
the monument was subject to limited reuse to store aviation fuel during World
War II. The built and earthwork structures in this monument are also a Grade
II Listed Building. The Listed Building also includes the built structures of
the battery's underground magazine and war shelter which are excluded from
this scheduling.
The battery's forward flank faces north west, its field of fire commanding the
deep water approach to the islands at the entrance to The Road. It has two
concrete emplacements for 6-inch breech-loading (BL) MK VII calibre guns set
into the rear of a rampart, behind which is a parade area called a terreplein.
Beneath the emplacements are an underground brick-vaulted magazine and a war
shelter reached by a concrete-faced light-well. The terreplein contains a
raised platform, called a traverse, containing a communications room and
supporting the Battery Commander's Position and range-finding post. The
emplacements, terreplein and magazine are contained within substantial
earthwork defences comprising a rampart around the forward and side flanks,
and a fully encircling outer ditch.
The concrete gun emplacements are situated 25m apart in the rear of the
rampart's forward flank. Each emplacement includes a raised podium around a
circular central recess which housed the central-pivot gun mounting. On its
forward side, the podium merges into the wider, slightly higher, rear face of
a broad concrete apron whose gently chamfered surface extends over the
adjoining rampart top. The rear faces of the podium have cast-in metal
brackets for handrail stanchions and contain recessed lockers to house shells
and cartridges required for immediate use; the metal handrails and locker
doors have not survived. Further lockers occur beside the podium in the
adjoining rear face of the apron; shell and cartridge lifts from the
underground magazine open at hatches in the rampart's concrete facing to each
side of the podium. A concrete terrace extends back from the podium, ending at
a sloping scarp down to the terreplein with access steps at each side. Beside
the inner flank of the emplacements, concrete steps rise from the terreplein
to the rampart crest. A flagstaff to the right of the north east emplacement
indicated when live firing was taking place.
Between the emplacements is a deep rectangular lightwell, partly recessed into
the rampart rear and retaining some original metal handrail stanchions along
its upper edge beside the terreplein. Steps descend from each end of the
lightwell to the battery's complex of underground structures which form that
part of the Listed Building excluded from this scheduling: these include a
brick-vaulted magazine originally with two cartridge stores and three shell
stores and shell and cartridge lifts, together with a two-roomed war shelter
and understair lockers.
Behind the emplacements and lightwell is the subrectangular levelled
terreplein, c.48m long, extending c.12m back from the emplacements and defined
by the rampart-face and by a wall to the rear. Behind the lightwell it is
paved to waterproof the underground structures beneath. The battery entrance
is near the north east end of the terreplein rear and is closed by its
original double steel gates, each with two loopholes and a reinforcing
framework bolted to the rear face. The gates open outwards, borne on rollers
engaged in curved rails.
The raised traverse extends into the terreplein from the rear wall, centred
slightly south west of the terreplein centre. The traverse has an ovoid plan,
c.20m long, and bulges to its maximum width of 7m towards its south west end.
It is revetted by concrete and contains a small communications room accessed
from behind the traverse. Records indicate the traverse was designed late in
the battery's construction, its original plan modified in 1901 to improve
cover against incoming fire from St Mary's Sound to the south west. The
traverse platform was designed to support a concrete parapet covering the
Battery Commander's Position; above the communications room a slender concrete
post formerly supported Watkin's depression range-finder (DRF) sighting
equipment. The DRF at this monument was calibrated by sighting onto a datum
post on Southward Well Point, off the south east of Samson. Close by the DRF
post on the traverse, a raised concrete structure with a recessed locker in
its rear face housed charts and an electric telegraph to record and transmit
DRF data to the gunners. The Watkins DRF at this battery was later replaced by
a position-finding cell built beyond this monument on the rampart of the
barracks/caretaker block to the south east. At the south west of the
terreplein, against the rampart rear, is a small latrine.
The battery's emplacements, magazine and terreplein are protected from
incoming fire and ground approach by extensive low-profile earthworks. The
earthworks include a rampart extending over the battery's site, with the
terreplein levelled into its rear and with the rampart's profile forming an
extension of the natural slope beyond the ditch. Along the inner lip of the
ditch the rampart measures 65m north east-south west by up to 40m wide and
rises to c.3m above the parade level at the gun emplacements. The broad
subrectangular ditch extends around the outer edges of the rampart and the
rear of the terreplein to protect all of the battery's operational structures
from ground approach. It is flat-bottomed, 7.6m wide at the base, ranges from
12m-20m wide at the lip, and measures 101m north east-south west by up to 74m
north west-south east externally; on the south east, behind the terreplein,
the outer edge of the ditch base almost merges with the natural slope beyond.
The ditch was designed to be filled with barbed wire entanglements secured by
retaining spikes: traces of the entanglements and spikes still survive at this
monument. The low profile of its earthworks rendered the battery more
difficult to locate and target for enemy gunners and masked both ditch and
emplacements from external view while allowing an unobstructed and wide field
of fire for the guns.
The Garrison's commanding position made it the focus for successive phases of
fortification on Scilly from the later 16th century. In the 1890s, a joint
army and navy review of the nation's coastal defences proposed the Isles of
Scilly should become an advanced naval signalling and re-fuelling station, to
be classed as a defended port, in view of their strategic position against
perceived threats from French Atlantic naval bases. Implementation of these
proposals between 1898 and 1901 produced two complementary gun batteries, this
monument and the Woolpack Battery 125m to the south east, to cover the deep
water approach to the islands and served by a barracks/caretaker's block
between them. Records indicate that the batteries' magazines held 500 rounds
per gun. The battery and the barracks defences reflect the latest
fortification designs and technology available at the time.
By 1902, the 6-inch guns of these batteries were felt to give inadequate
defence against motor torpedo boat attack; a proposed third 6-inch gun battery
was abandoned in favour of two 12-pounder quick-firing gun batteries, one
above Steval Point, 100m WNW of this monument, the other at Bant's Carn on the
north western coast of St Mary's. Other structures of the defensive system in
which this monument operated include coastal searchlight emplacements and
their control posts at Woolpack and Steval Points, with their electricity
supply generator housed in an 18th century battery between them. An
artificer's workshop for the maintenance of the batteries' guns and mountings
survives near the summit of The Garrison, 190m ESE of this monument.
During construction of these defences, national defence policy underwent a
radical shift. German power replaced that of France as the dominant threat, a
re-orientation strengthened by the signing of the Entente Cordiale in 1904. In
the resulting re-alignment of the nation's defences to the east, detailed in
the Owen Report of 1905, the Isles of Scilly were abandoned as a naval station
and, with little commercial importance, they also lost their defended port
status. Consequently, though these batteries had been used for coastal defence
training, their guns were dismantled in 1906 and by 1910 had been removed for
storage in Falmouth.
During World War II, The Garrison housed a radar cell and aviation fuel
stores. The Steval Battery's underground complex was used to store aviation
spirit after bombing raids in 1940 threatened its former location on Hughtown
The battery's underground complex comprising its magazine, war shelter and
lockers, are excluded from the scheduling but the ground beneath and above
them is included. The modern club house and all modern fittings, wooden rails,
the modern shooting range enclosure on the terreplein and its rear wall
linking the traverse with the rear of the south west emplacement, and all
dumped modern refuse are excluded from the scheduling but the ground beneath
them is included.

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

Source: Historic England

Reasons for Scheduling

The Isles of Scilly, the westernmost of the granite masses of south west
England, contain a remarkable abundance and variety of archaeological remains
from over 4000 years of human activity. The remote physical setting of the
islands, over 40km beyond the mainland in the approaches to the English
Channel, has lent a distinctive character to those remains, producing many
unusual features important for our broader understanding of the social
development of early communities.
Throughout the human occupation there has been a gradual submergence of the
islands' land area, providing a stimulus to change in the environment and its
exploitation. This process has produced evidence for responses to such change
against an independent time-scale, promoting integrated studies of
archaeological, environmental and linguistic aspects of the islands'
The islands' archaeological remains demonstrate clearly the gradually
expanding size and range of contacts of their communities. By the post-
medieval period (from AD 1540), the islands occupied a nationally strategic
location, resulting in an important concentration of defensive works
reflecting the development of fortification methods and technology from the
mid 16th to the 20th centuries. An important and unusual range of post-
medieval monuments also reflects the islands' position as a formidable hazard
for the nation's shipping in the western approaches.
The exceptional preservation of the archaeological remains on the islands has
long been recognised, producing an unusually full and detailed body of
documentation, including several recent surveys.

The distinctive form of gun batteries developed at the end of the 19th century
differed fundamentally from earlier batteries and provided the first
application of principles that came to dominate the design of such defences in
the 20th century.
Their design and location reflects major developments in armament technology,
strategic thought, the nature of the perceived threat and defensive policy. By
the mid 1880s the development of an effective breech-loading system had
considerably improved the speed of re-loading guns. Hydraulic and compressed
air systems enabled the recoil of guns to be absorbed, allowing guns to be
located on fixed centrally pivoted mountings which improved accuracy and speed
of firing. Hydraulics were also deployed for ammunition supply from magazines.
Lighter steel barrels and improved propellants gave greater muzzle velocities
and range without requiring corresponding increases in gun size and weight,
thereby increasing the manoeuvrability of the guns while the deployment of
brass cartridge cases further increased the speed of re-loading. The invention
of smokeless powder reduced the visibility of guns on firing. Coupled with
these advances, the development of new range-finding equipment and electrical
communications considerably increased the speed and accuracy of target
position finding and the control and coordination of armament. These
technological changes revolutionised the nature of field fortification
considered appropriate to house the guns. Priority was given to open
emplacements with fixed gun mountings and low profile earthwork fortifications
which were hard to target while allowing the guns maximum manoeuvrability;
defence against close quarters ground approach was provided by the newly-
developed barbed wire entanglements in concealed ditches, reinforced by
machine-gun and rifle fire across the unobstructed ramparts. The gun
emplacements were served by underground magazines with hydraulic hoists. Early
applications of these new principles of fortification were made in the later
1880s in the rather different context of infantry reboubts in south east
England, their form characterised as the `Twydall Profile'. During the 1890s
variants and developments of the Twydall Profile dominated new land
fortifications for infantry and artillery, providing a major influence on the
design of the defences constructed on the Isles of Scilly during its 1898-1906
phase of fortification.

The Steval Battery has survived well, preserving much of the original form of
both its earthwork and built structures with limited modifications present in
those parts of the underground complex excluded from this scheduling. Such
intact survival of a battery from this phase is rare and of much importance
for our knowledge of the development of modern artillery defences. Most other
components in The Garrison's contemporary defensive system, that included this
battery as a major integral part, survive well. Spatially, the rare survival
of such a complete defensive system allows the relationships of its components
to be studied against their armament capabilities and the strategic methods by
which those defences were intended to be used, in the controlled background of
a single location. The system of defences to which this monument contributed
was directly inspired by considerations of national defence; as such it also
has a wider historical importance whose immediate context is defined by the
national defence reviews which led to the implementation and later the
abandonment of the naval base which this battery was designed to protect.

Source: Historic England


Books and journals
Saunders, A D, Fortress Britain, (1989)
Saunders, A D, Fortress Britain, (1989)
Stevenson, I V, Some West Country Defences, (1989), 11-26
1358-0/3/89, DNH, List of Buildings of Special Architectural or Historic Interest, (1992)
1901-2; now in Public Record Office, Edwards, H, Measured plans and sections made on completion of battery, (1901)
Dated 1/9/1993, with drawing & notes, St Mary's Rifle and Pistol Club, LB Consent Application to Isles of Scilly Council, Appl No. 3579, (1993)
Information given to MPPA by phone from Dick Linzey, 1/9/1995, (1995)
J Guy, Fortress Study Group, Letter to J Ratcliffe re. Scilly defences 1902-10, 1993, Letter dated 3/11/1993
Parkes, C/CAU, Scilly SMR entry for PRN 7908, (1994)
Parkes, C/CAU, Scilly SMR entry for PRN 7908.04, (1994)
Parkes, C/CAU, Scilly SMR entry for PRN 7909, (1994)
Report for Cons SW, Feb 1994, Linzey, R and EH Architecture Branch, Recs for Incr Statutory Protectn to Woolpack & Steval Batteries, Cons SW, (1994)
Title: 1:25000 Ordnance Survey Outdoor Leisure Map, No. 25: Isles of Scilly
Source Date: 1982

Source: Historic England

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