Summary
Four concrete Second World War search light emplacements on the shore in front of Fort Bovisand (qv.).
Reasons for Designation
The Four Coastal Artillery Search Lights (CASLs) are listed at Grade II, for the following principal reasons:
* Historic interest: they have strong cultural and historical significance, within both a local and national context, marking the improvement in search light technology during the Second World War to defend against enemy attack.
* Rarity: it is uncommon for CASLs to survive well in such a grouping on the shoreline.
* Intactness: despite some damage and decay to the fabric, and the removal of some doors and fittings, the majority of the fabric remains intact and legible.
* Group value: the structures form an historic group with each other, Fort Bovisand and related structures, and with the Staddon Heights military landscape as a whole.
History
The fortifications around the port of Plymouth and the naval base at Devonport have expanded and been modified steadily as weapons technology has advanced, and as military threats have changed. In the late C15 and early C16, small blockhouses were built along the cliffs of Plymouth Hoe. By 1600, Plymouth Fort was built where the Royal Citadel now stands, and Drake's Island was better fortified. The earliest known fortifications at Staddon Heights are shown on a map of c.1587, where a barricade and cannon are depicted. During the C18, the almost continual wars with France saw the expansion of Plymouth's defences, including on Staddon Heights in the east, and Maker Heights in Cornwall. Staddon Battery was built in 1779 to protect the approach to Plymouth Sound from the east, and had a clear view over the approach to Plymouth Sound by sea. A breakwater was built at the entrance to the Sound, to the designs of the renowned engineer and bridge builder John Rennie (1761-1821), with construction beginning in 1811. The mile-long protective breakwater, his grandest executed work for the Admiralty, was not completed until 1848, although its scale was admired by Napoleon when he arrived as a prisoner at Plymouth in 1815, to Rennie's gratification. The breakwater was completed by his son, Sir John Rennie (1794-1874), who also built Bovisand Pier and Harbour (1816-24), which watered ships via a nearby reservoir, thereby easing the increasing traffic congestion in the port of Plymouth. Staddon Battery was disarmed in 1853 following the completion of Staddon Point Battery (qv.) to the south in 1847, although it may have continued to be used by the military after this time.
The mid-C19 was marked by a period of growing political and military concerns over French foreign policy and the development of an arms race between the two nations. The Royal Commission of 1859 considered the need for modern defences to protect Royal Dockyards, ports and arsenals; their recommendations for Plymouth resulted in the completion of six new coastal batteries and a ring of eighteen land forts and batteries. These were based on three principal forts which are located at Tregantle on the Cornish side of Plymouth harbour, and Crownhill and Staddon on the Devon side. The land forts and batteries were linked by a system of military roads protected from the likely direction of attack by earth traverses and cuttings. Fort Staddon was built between 1861- 69 as the main work of the Staddon Heights defences. It occupies the highest point between valleys leading to Hooe Lake and Bovisand, and lies between Fort Stamford and Brownhill Battery. Further defence works included Breakwater Fort (qv.) from 1861, which was built 100 yards behind the centre of the breakwater, and Fort Bovisand (qv.), built below Staddon Point Battery between 1861 and 1871.
Searchlights were used for military purposes from the 1880s and by the turn of the century their usefulness as part of coastal defences was firmly established. They were primarily used to spot and track approaching enemy vessels. Their deployment was of particular use when tackling the threat of submarine attack, a form of marine vessel that developed rapidly in the later C19. By 1880 the key English strategic target of Plymouth was defended by anti-submarine mines laid between the Breakwater and Bovisand Pier (qv.) to the east, and Fort Picklecombe (qv.) to the west. Defence Electric Light Positions (DELs) and a submarine mine observation station were built to the north of the fort and on Bovisand Pier between 1896 and 1900. Two further DELs were built in c.1910 to the south-east of the fort. Searchlights were used in World War One when Plymouth Sound was infiltrated by German U-boats. Booms were spread across the Sound entrances, one of which had its shore end at Bovisand. The south DEL on the shore was still in use in 1915, and the searchlights at the seaward end of the pier were relocated to a blockhouse at its landward end in this year.
In the lead up to the Second World War, preparations were made once more for enemy action, and in 1939 there were four Coastal Artillery Search Lights (CASLs) in emplacements at Bovisand. Two were on the road to the fort and two in the early-C20 blockhouse at the base of the pier. Plymouth was heavily bombarded from the air in March and April 1941, and although the fort guns were unsuitable for targeting the German bombers, the search lights in CASLs could distract enemy pilots and pinpoint their locations. This drew enemy fire on some occasions and there were two direct hits on the fort, although neither bomb exploded. As the Second World War progressed, the Staddon defences were upgraded when a number of batteries were reconfigured, improved artillery was installed, and new ancillary structures such as six further CASLs were built. They served the pair of new, advanced twin 6-pounder guns that were installed on top of the casemates of the fort in early 1942. The rapid-fire guns could fire 70 rounds per minute from twin barrels and were needed to engage German E-boats (motor-torpedo boats) in case they attacked the Sound. Due to problems supplying the barrels they were not functional until early 1943. The lights were powered from engine rooms in Casemate Nos. 1, 2 & 3, and controlled from the emplacements above the casements. CASL Nos. 3, 4, 5, & 6 were fixed beam.
The guns and searchlights at Bovisand were removed in 1957 when the fort closed as a military establishment. While some of the buildings on the site have found new uses, many of the smaller structures have remained out of use since the War, or prior to that if their function had become obsolete beforehand. One of the DELs at the end of the pier was demolished in the 1970s and the other has been adapted for use by a diving school, but is since redundant. Part of Fort Bovisand and the harbour have served as commercial diving schools for periods from 1970 to the early C21.
In 2013, four of the CASLs remain intact and disused. CASL No.3 (original terminology) is in front of Casemate 17, built into the seawall that stretches west to incorporate the pier. CASL No. 4 is in front of Casemate 20 and has had a small lighthouse built on its roof. CASL No.5 is opposite Casemate 23. CASL No. 6 is further along the shore, beyond a modern stone embankment with gabions, supporting the road above. The curved rubble stone-lined base of CASL No.1 stands close to the roadside above and between CASL No. 5 and CASL No.6. The remains of CASL No.2 may lie further along the road to the north-east, hidden below undergrowth. CASLs No. 1 and No. 2 may have been built on the earlier sites of two former DELs of 1910. The early C20 blockhouse that was the site of two CASLs of 1939 had been taken out of use for searchlights in 1942, was much altered in the late C20, and is derelict in 2013.
Details
Four Coastal Artillery Search Light emplacements of 1941 (CASL Nos. 3, 4, 5 & 6), historically associated with the two twin 6-pounder emplacements at Fort Bovisand (qv.)
MATERIALS: shuttered concrete with steel grilles and doors to some openings. The emplacements stand on worked, cliff-face rock and concrete bases.
DESCRIPTION:
CASL No. 3 is rectangular on plan with an attached blast entry to the north. It is built into the early-C19 seawall and the bank behind. The south-east (seaward) wall is canted and has two vertical rectangular openings. To the rear are steps leading up to the fort, and within the blast entry is an intact steel door with three strap hinges. On the roof is a circular hole for ducting heat from a searchlight. The interior is split into two cells. There are electrical fittings of 1942 date.
CASL No. 4 is rectangular on plan with an attached blast entry to the east. To the rear are steps leading up to a platform, and further steps up to the fort. On the platform is a modern lighthouse structure. The south-east (seaward) wall is canted and has two vertical rectangular openings with grilles. The interior is a single cell with modern inserted tanks of breeze block. On the roof is a circular hole for ducting heat from a searchlight.
CASL No. 5 is rectangular on plan with an attached blast entry to the north-east. The south-east (seaward) wall is canted and has three vertical rectangular openings with grilles. The doorway within the blast entry has double steel doors, one of which is collapsed but in situ. On the roof is a circular hole for ducting heat from a searchlight.
CASL No. 6 is rectangular on plan with an attached blast entry to the north. The steps leading up to the fort road at the rear are obscured by undergrowth. The south-east (seaward) wall is canted and has three vertical rectangular openings with grilles. The low doorway within the blast entry had double steel doors, although one has been removed. There is an inserted cupboard fitted in the north-east corner.
Later C20 structures have been inserted within the envelope of CASL No.3, and on the roof of CASL No.4. Pursuant to s.1 (5A) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (‘the Act’) it is declared that the later C20 structures are not of special architectural or historic interest. Furthermore, the paths and steps around the CASLs are altered and not of special interest, and therefore excluded from the listing.
