Second World War HAA Gun Site, TN9, Sandpit Hill (EHER 16189)

Remains of a World War II Heavy Anti aircraft gun site sited on Sandpit Hill north of Benfleet Creek and Hadleigh Marsh along the Thames estuary. Remains include four 5.25 inch gun emplacements and the associated remains of Nissen huts. To the west lies a post war combined Operations Room and Generator Block. 500 metres to the south are 4 octagonal 4.5 inch gun emplacements set in a semi circle each having 5 ammunition recesses built into the surrounding walls and flanked by an integral bomb proof shelter. A second on site magazine located partly below ground level is located to the west of this. Further remains include a Command Post, the Gun Store, and a water tower. Scheduled.

Original HER entry merged with NRHE data import: Two WWII anti-aircraft batteries visible on aerial photographs. The first, at TQ 800 865, comprises of four-gun emplacements and a central command post. This appears to have been replaced by a later site at TQ 803 866. <1> - <3> Documented in contemporary records as "TN9 Hadleigh", a WWII Heavy Anti-Aircraft gun site on Sandpit Hill, south-west of Hadleigh. Equipment and manning at the site is documented at various dates: 30 Apr 1940: Guns-4 x 4.5", Regt-59, Bty-164. 2 Jun 1940: Guns-4 x 4.5", Bty-164. 20 May 1942: Guns-4 x 4.5", Radar-none, Regt-2, Bty-11. 22 Jun 1942: Guns-4 x 4.5", Radar-none. 9 Dec 1943: Regt-184(M), Bty-625. 2 Nov 1944: Guns-4 x 5.25". 15 Jan 1946: . An aerial photograph taken in May 1946 shows the gun emplacements at two distinctly separate sites. The 4.5" positions are centred at TQ 8002 8647. There are four octagonal emplacements in a semi-circle facing east. Each has five ammunition recesses and an external integral shelter. In the centre of the semi-circle is a number of buildings and structures including the command post. What appears to be on-site magazine bunkers are situated one to the south-east and one to the west of the emplacements although identification of these is not positive. Centred at TQ 8034 8659, some 250 yards to the north-east, are the 5.25" gun positions, in a square formation. The circular gun platforms can be seen with their integral rectangular structures containing the computer, powerhouse, war shelter and gun store. Between and to the north of the two-gun sites is the accommodation site centred at TQ 8014 8664. Around 30 buildings and structures can be made out. <4> - <6> Aerial photographs. <7> <8> Photos taken of the site. <9> - <11> September 1998. Field visit The 5.25" gun emplacements have been filled in with soil and grassed over although the area is easily distinguished by its high, rounded profile. One part of an emplacement, the north-easternmost of the four at TQ 8037 8660, shows the outer rim of the ammunition gallery above ground level although not enough can be seen to determine overall details. To the west of the 5.25 site at TQ 8026 8663 is, apparently, a combined Operations Room/Generator Block. This survives intact, measuring 50' long with the narrower, Operations, end 14' wide. It is built of heavy concrete with steel-framed, shuttered windows and is of the same basic type as the 5.25 site at "ZE4 Buckhurst Hill" (EHER 10376) although there the two buildings are separate. The building at Hadleigh does not appear in its current form on the 1946 aerial photograph referred to above and must have been built after that date. The 1946 photograph shows a similarly aligned building on the same site but apparently half-open to the sky, possibly an earlier command post for the 5.25's. On the hillside towards the 4.5" site are three small buildings. Two are simple, one-roomed structures but the third, at TQ 8005 8657, is a larger, more substantial, building. It is constructed of concrete with a heavy steel door and four steel-framed, heavily shuttered windows on the south side. This was clearly the Gun Store as it follows virtually the exact pattern as that still signed as such at "TN10 Vange" (EHER 14748). It can be seen from aerial photographs that the two northernmost 4.5" emplacements were demolished between 1946 and 1960. The remaining two have been filled in with soil but, like the 5.25" emplacements, the area can be distinguished by the high profile of grassland. Parts of the emplacement walls can be seen where the grass and soil have eroded away. To the west of the 4.5" site, at TQ 7998 8647, what was almost certainly the On-Site Magazine is extant as a shooting club building although it was not possible to access the area at the time of the site visit. During and after World War Two, TN9 Hadleigh was a complex site of 5.25" and 4.5" gun emplacements, ancillary buildings and structures, and accommodation huts. All of the accommodation huts have been demolished, and the appearance of the site has changed with the addition of a banked reservoir and heaped soil and grass over the gun positions. However, potentially much remains. On the surface there is the post-war Operations Room/Generator Block, rare in the county. The Gun Store is one of only two - the other is at TN10 Vange (EHER 14748). The On-Site Magazine is similarly one of only two - the other is at ZE7 Lippitts Hill (EHER 10374). Two of the 4.5" emplacements and their command post may remain beneath the soil. But, of major importance as no emplacements of this gun calibre remain in Essex, the three/four-star grading reflects the probability that the 5.25" emplacements remain intact or semi-intact beneath the ground. <12> 2001. Assessment. At Hadleigh the standby generator building and attached operations room have been identified as post-War in date. This building is associated with surviving Second World War structures, including buried 5.25-inch gun emplacements pits, which probably survive as archaeological remains. Closer analysis of this site may reveal further post-War modifications. <13> March 2001. Designation. The monument is in eight areas of protection. The first includes the four 5.25 inch gun emplacements sited in a square formation and the remains of associated Nissen huts. The emplacements mostly survive below ground, having been infilled with soil. The outer edge of the north easternmost emplacement's ammunition gallery is visible above ground level. Their design is known from aerial photographs, the earliest of which dates to 1946 and shows the circular gun platforms with their internal rectangular structures. The gun site’s ammunition supplies were stored in nine ammunition huts positioned in a row to the immediate north-west of the emplacements. The bases of two of these huts survive and are included in the scheduling. The surviving concrete floor of the huts carries the impression of the corrugated sheeting originally used for the superstructure. The second area to the west of the 5.25 inch emplacements is a combined Operations Room/Generator Block. This structure is built of heavy concrete with steel-framed, shuttered windows and measures some 22m long and a maximum of 15m wide. It belongs to the post-war period when the 5.25 inch gunsight was upgraded as a response to the Cold War threat and replaced an earlier wartime building. The third area, which encloses the 4.5 inch gun emplacements and associated structures, lies some 500m to the south west of the larger guns. Aerial photographs taken in 1946 show four octagonal emplacements in a semi-circle facing east towards the direction of incoming enemy aircraft. Each has five ammunition recesses built into the internal faces of the surrounding walls and is flanked by an integral bomb-proof shelter for the gun crew. In the centre of the semi-circle are a number of buildings and structures, including the command post. Now partly infilled, the two most southerly emplacements have concrete enclosures still visible. The foundations of the other two emplacements and elements of the command post and on-site magazine will survive as buried features. The fourth designated area lies to the west of the 4.5 inch emplacements and associated structures and encloses a second on-site magazine. This is a flat roofed concrete structure, partly below ground level, measuring some 15m by 8m. Four more protected areas lie in between the two sets of emplacements and enclose four ancillary buildings: the first is the Gun Store, two are simple, one-roomed structures, and the fourth is a water tower. The Gun Store is constructed of concrete, with a heavy steel door and four steel-framed, heavily shuttered windows on the southern side. The accommodation area for the gun crews (a series of lightweight barracks formerly located in between the two sets of gun emplacements) are not included in the scheduling. War Office documents relating to the equipment and manning of gunsight TN9 Hadleigh indicate that the four 4.5 inch guns were operational from 1940, whilst the four 5.25 inch guns came into operation during the course of 1944, with the latter being maintained as a Cold War deterrent during the post-war period. <14> 2010. Topographic survey and historic landscape assessment. During the Second World War the Site was re-used as an anti-aircraft battery, troop camp, searchlight position and pigeon breeding lofts, with these buildings depicted on the 1955 map. Following the Second World War the Sandpit Hill anti-aircraft battery was upgraded as a response to the Cold War threat, becoming part of the Nucleus Force, which disbanded in 1955, after which the Site was abandoned. Part of the Site was re-used as a motocross track during the 1960s and 1970s, which is visible on aerial photographs but not published on OS mapping from that era. <15> <16> May 2011. Watching brief. The concrete pads were revealed in a section of cable trench to the north-west of the cabin. They sat flat in the topsoil, around 3.5m apart and measured 0.5m square and 0.15m thick. The lead pipes passed beneath the concrete access road to the west of the TER/CER cabin. The amount of archaeological remains found by the monitoring is small and suggests that the accommodation area mainly comprised lightweight buildings with either shallow or no foundations, perhaps a combination of large sheds and Nissen huts. This is supported by the concrete pad foundations for building A. The buildings of the accommodation area which still stand are constructed from concrete and brick and were perhaps left in situ because they were in better condition or more difficult to demolish. <17> May 2012. Rectified photography. The combined operations room/generator block, and the gun store were photographed; the report contains georectified imagery. The buildings were also assessed for their condition. There are no visible signs of camouflage paint to the exteriors, but there is graffiti on the South elevations of both buildings. At the time of the survey the building was partially surrounded with Heras fencing. The generator block is a large square structure built from shuttered concrete with a flat concrete roof, large armour-plated doors on the south elevation and heavy iron vents on the other two sides. The operations room is a low linear structure built from shuttered concrete with a flat concrete roof, armour-plated doors and windows and entry from the South and east elevations. A large modern shed obscures much of the north elevation. The gun store is a low square structure built from shuttered concrete with a flat concrete roof, armour-plated doors and windows, with entry from the east and south elevations. Camouflage paint in the form of wide green and black irregular vertical bands, survives on all elevations, but only the south and east elevations are affected by graffiti. <18> See also: <19> <20>