Heavy Anti-aircraft gunsite on Sandpit Hill


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:


Ordnance survey map of Heavy Anti-aircraft gunsite on Sandpit Hill
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This copy shows the entry on 17-Oct-2019 at 21:18:34.


The building or site itself may lie within the boundary of more than one authority.

Castle Point (District Authority)
National Grid Reference:
TQ 79977 86471, TQ 80026 86596, TQ 80044 86467, TQ 80047 86694, TQ 80050 86572, TQ 80062 86627, TQ 80259 86632, TQ 80326 86594

Reasons for Designation

Although of comparatively recent date, 20th century military sites are increasingly seen as historic survivals representing a defining episode in the history of warfare and of the century in general; as such they merit careful record and, in some cases, preservation. One of the more significant developments in the evolution of warfare during this period was the emergence of strategic bombing in World War II, and this significance was reflected by the resources invested in defence, both in terms of personnel and the sites on which they served. During the war, the number of people in Anti-aircraft Command reached a peak of 274,900 men, additional to the women soldiers of the ATS who served on gunsites from summer 1941, and the Home Guard who manned many sites later in the war. A national survey of England's Anti-aircraft provision, based on archive sources, has produced a detailed record of how many sites there were, where they were and what they looked like. It is also now known from a survey of aerial photographs how many of these survive. Anti-aircraft gunsites divide into three main types: those for heavy guns (HAA), light guns (LAA) and batteries for firing primitive unguided rockets (so called ZAA sites). In addition to gunsites, decoy targets were employed to deceive enemy bombers, while fighter command played a complementary and significant role. Following the end of World War II, 192 HAA sites were selected for post-war use as the Nucleus Force, which was finally closed in 1955. The HAA sites contained big guns with the function of engaging high flying strategic bombers, hence their location around the south and east coasts, and close to large cities and industrial and military targets. Of all the gunsites, these were the most substantially built. There were three main types: those for static guns (mostly 4.5 and 3.7 inch); those for 3.7 inch mobile guns; and sites accommodating 5.25 inch weapons. These were all distinct in fabric, though they could all occupy the same position at different dates, or simultaneously by accretion. As well as the four or eight gun emplacements, with their holdfast mountings for the guns, components will generally include operational buildings such as a command post, radar structures including the radar platform, on-site magazines for storing reserve ammunition, gun stores and generating huts, usually one of the standard Nissen hut designs. Domestic sites were also a feature of HAA gunsites, with huts, ablutions blocks, offices, stores and amenities drawn from a common pool of approved structures. Sites were often also provided with structures for their close defence; pillboxes are the most common survivals, though earthwork emplacements were also present. The layout of HAA gunsites was distinctive, but changed over time, for example to accommodate the introduction of radar from December 1940, women soldiers from summer 1941, and eight gun layouts from late 1942. Nearly 1,000 gunsites were built during World War II, and less than 200 of these have some remains surviving. However, at only around 60 sites are these remains thought sufficient to provide an understanding of their original form and function. This includes 30 of the 192 examples which continued in use until 1955. Surviving examples are therefore sufficiently rare to suggest that all 60 well preserved examples are of national importance.

The Heavy Anti-aircraft gunsite on Sandpit Hill is an exceptional survival of its type in the country. The importance of the site lies in its complexity and range of surviving gun emplacements and ancillary buildings. It not only retains gun emplacements of the 4.5 inch variety (and also their associated structures), but also a complete battery of 5.25 inch emplacements (and associated structures), the latter being the only survivals of this gun calibre in the county. In addition it also has an exceptional collection of ancillary buildings, including a Gun Store (one of only two in the county), a well-preserved on-site magazine adjacent to the 4.5 inch emplacements and the post-war combined Operations Room and Generator Block.

Considered together with all other variations of Heavy Anti-aircraft gunsite design, TN9 Hadleigh is one of only nine sites to survive (in any form) from an original wartime deployment of about 40 HAA positions across Essex - a pattern designed to combat German bombers en route to the capital, the Thames estuary and other military targets in the south east of England. It provides an exceptional insight into the development of anti-aircraft measures in the region and is a significant, visible reminder of the nature of home defence during World War II.


The monument includes the remains of a World War II Heavy Anti-aircraft gunsite, documented in wartime records as `TN9 (Thames North) Hadleigh', which is sited on a ridge of high ground known as Sandpit Hill, located to the north of Benfleet Creek and Hadleigh Marsh along the Thames estuary.

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 emplacements have three levels: the upper level has the ammunition gallery from where the crew loaded the gun; the spent cartridge trench forms the next level (this includes a tunnel to the outside down which the spent shell cases were disposed); the pit at the lowest level houses the power mechanism. The gunsite'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 gunsite 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 gunsite 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.

All modern fence posts are excluded from the scheduling, although 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:
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Books and journals
Dobinson, C S, Twentieth Century Fortifications in England: Volume 1.3, (1996)
Dobinson, C S, Twentieth Century Fortifications in England: Volume 1.3, (1996), 469-472
Dobinson, C S, Twentieth Century Fortifications in England: Volume 1.3, (1996), 469-472
Nash, F, World War Two Heavy Anti-Aircraft Gun Sites in Essex, (1998)
Nash, F, World War Two Heavy Anti-Aircraft Gun Sites in Essex, (1998), 57-8
CBA, , 'CBA' in Twentieth Century Fortifications in England, (1996), 469-472
HQ 6th AA Division Location List, (1940)
June, Hunting Surveys Ltd., Run 37-052, (1960)
June, Hunting Surveys Ltd., Run 37-052, (1960)
May, RAF, 106G-UK 1496-4388, (1946)
Tyler, S, MPP Film , (2000)
Tyler, S, MPP Film, (1998)
Tyler, S, MPP Film, (1998)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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