Four Palmerstonian Gun Batteries, Flat Holm

Cadw's description

Summary description and reason for designation

The monument comprises the remains of four Victorian coastal batteries built on Flat Holm, an island located 4.5km south-east of Lavernock Point in the Bristol Channel. The batteries were built following the publication of The Royal Commission on the Defence of the United Kingdom report in 1860 that recommended upgrading the nation’s coastal defences against possible invasion by the French Navy of Napoleon III. They were known as Palmerston’s Forts or Follies being named after the Prime Minister that promoted their construction. Flat Holm formed part of a new defensive line across the Bristol Channel from Lavernock Point, Glamorgan to Brean Down, Somerset, including the neighbouring island of Steep Holm. On Flat Holm’s western side, the gun batteries at Castle Rock and Farmhouse batteries faced north-west over the northern shipping lane to Cardiff and Newport to provide cross-fire with the guns from Lavernock Point; the guns at Well and Lighthouse batteries on the southern side faced southwards across the middle shipping lane to Bristol and Avonmouth to provide a cross-fire with guns on Steep Holm. The War Office purchased land in 1865 and the contract to build the batteries was signed with John Perry of Weston-super-Mare on 17 February 1866. The works were completed in July 1871 at a cost of £12,844. The four batteries were equipped with nine medium-sized Naval 7-in Rifled Muzzle Loading (RML) Mk III guns manufactured in Woolwich and brought into service in 1868. Each gun could fire a shell weighing 52kg capable of penetrating 200mm of armour at 1,000m. Unusually, the guns were mounted on Moncrieff ‘Disappearing’ Mk I garrison carriages and protected in sunken emplacements owing to the island’s low, flat and exposed topography, which enabled them to be hidden until the moment of firing, when they were raised using a counterweight; the recoil brought the guns back down into the pit to be reloaded safely out of sight. The 1881 and 1891 Censuses recorded a Master Gunner, his family and a small number of gunners from the Coast Brigade, Royal Artillery present on the island, who would be supplemented by Artillery Volunteers during conflict. The guns were decommissioned and dismounted in 1903. The mounts were cut up and recycled. The guns survive in varying states of preservation: one complete gun and the barrels of four others were recycled, but those at Well and Lighthouse batteries were left on the island near their original emplacements. The gun from Well Battery was subsequently removed to Beachley Barracks, Gloucestershire in 1964.

Castle Rock Battery (Item A) was located on the northern headland of the island on the cliff top. It consisted of three brick and stone-lined circular gun emplacements set into a lobed and flat-topped earthen protective mound. The central emplacement was open backed, whilst those to the north and south were fully enclosed and accessed via vaulted passageways. The buried magazine was brick and stone-built and located to the east of the gun emplacements. It comprised a dog-legged passage accessed via separate northern and southern entrances opening on to two buried magazine chambers, with a physically separate lamp passage located to the east. The northern chamber was altered into an air raid shelter during the Second World War, with a dedicated roof escape hatch. The cut-off butt-ends of the RML guns survive on the north edge of the earthwork, central emplacement gun floor and by the southern emplacement rim respectively. The battery’s boundary was marked by War Department boundary stones Nos. 5-7. The alignment of the boundary fence remains discernible as a low earthwork and there is a surviving iron fencepost next to boundary stone No. 5.

Farmhouse Battery (Item B) was situated on the western side of the island. It consisted of two brick and stone-built gun emplacements set into a lobed and flat-topped earthen protective mound. The southern emplacement was enclosed, whilst the northern emplacement was open backed, being converted during the Second World War into a shed for a generator and associated air raid siren. The brick-built passageway between the two gun emplacements accessed the cartridge store. The east-facing vaulted passageway between the two emplacement entrances accessed the shell store. The remains of both RML guns survive as cut-off butt-ends located on the earthworks above their respective gun emplacements. The battery’s boundary was marked by War Department boundary stones Nos. 1-4.

Well Battery (Item C) was located on the south-western side of the island. It consisted of a single open-backed emplacement surrounded by a rounded and flat-topped protective earthwork. Separate entrances on the southern side of the emplacement provided access to the cartridge and shell stores. The roofless remains of the associated small arms shed survive to the north of the entrance. The battery’s boundary was marked by War Department boundary stones Nos. 34-38.

Lighthouse Battery (Item D) was located on the higher south-eastern corner of the island within the fortified area defined by the scheduled rock cut ditch and rampart (GM632). A single enclosed emplacement to the south-east of the lighthouse was linked by a raised earthwork bank to a pair of emplacements – one open and one enclosed – and magazine to the south-west of the lighthouse. The eastern emplacement was accessed via an excavated ramp leading through a vaulted passage. The gun survives intact, located on the south-eastern rim of the emplacement. The earthwork to the north of the emplacement was adapted to receive a square Second World War concrete structure, most probably a weapons pit. An open excavated passageway provided access to the western pair of emplacements set within their bi-lobed earthwork to the south and the buried magazine to the north, which was of similar design to that at Castle Rock Battery. The emplacements’ guns both survive intact on the protective earthwork. The roofless remains of the Victorian small arms shed survive to the north of the linking earthwork. During the Second World War, the floors of the western pair of gun emplacements were adapted to receive temporary hutting to house generators; these survive as concrete foundations and wall ends. The southern part of the protective earthwork was utilised by a Second World War Battery Observation Post (scheduled separately as GM595) and a Fire Command Post, surviving as a concrete foundation, was built into the linking bank.

The monument is of national importance for its potential to enhance our knowledge of nineteenth century coastal defence practices. The monument is well preserved and is an important relic of actions taken against the perceived threat of naval attack in and above the Bristol Channel. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The importance of the monument is enhanced by the group value it shares with other Victorian defensive structures on the island, including the defensive rock-cut ditch and rampart (GM632) and rainwater catchment (GM633), and its subsequent partial re-modelling for a later combined coastal and heavy anti-aircraft defensive scheme during the Second World War (GM595). The monument’s importance is further enhanced by the survival of contemporary documentation detailing the context, construction, operation and closure of the defences.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive. Originally scheduled in 1974 as ‘Three Palmerstonian Gun Batteries, Flat Holm,’ the scheduled area has been extended to cover the missing elements of the three scheduled batteries (typically including the protective earthworks, magazines and War Department boundary stones) and to include the fourth (Well) battery, which were all parts of the War Department’s original design. Consequently, the scheduled monument has been renamed as ‘Four Palmerstonian Gun Batteries, Flat Holm.’ Scheduled area ‘A’ is an irregular rectangle centred on OS NGR 322042 165120 and measures 74m NE-SW by 60m transversely. Scheduled area ‘B’ is an irregular rectangle centred on OS NGR 321902 165001 and measures 56m NE-SW by 39m transversely. Scheduled area ‘C’ is an irregular rectangle centred on OS NGR 321973 164717 and measures 80m E-W by 55m transversely. Scheduled area ‘D’ is an irregular polygon centred on OS NGR 322211 164645 and measures 138m E-W by 73m transversely.