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


Heritage Category: Scheduled Monument

List Entry Number: 1014784

Date first listed: 01-Aug-1996


Ordnance survey map of Late 19th-early 20th century Steval Battery on The Garrison, St Mary's
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The building or site itself may lie within the boundary of more than one authority.

District: Isles of Scilly (Unitary Authority)

Parish: St. Mary's

National Grid Reference: SV 89703 10329


Legacy Record - This information may be included in the List Entry Details.

Reasons for Designation

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' settlement. 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.


Legacy Record - This information may be included in the List Entry Details.


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 Pier. 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.

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.

Legacy System number: 15437

Legacy System: RSM


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 Author: Publisher: Surveyor:

End of official listing