World War II anti-aircraft rocket battery and bombing decoy control building 265m north east of Ashridge Farm


Heritage Category:
Scheduled Monument
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Date first listed:


Ordnance survey map of World War II anti-aircraft rocket battery and bombing decoy control building 265m north east of Ashridge Farm
© Crown Copyright and database right 2019. All rights reserved. Ordnance Survey Licence number 100024900.
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The building or site itself may lie within the boundary of more than one authority.

Sedgemoor (District Authority)
National Grid Reference:
ST 46852 56110

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 ZAA batteries for firing primitive unguided rockets or unrotated projectiles (UPs). In addition to gunsites, decoy targets were employed to deceive enemy bombers, while fighter command played a complementary and significant role. The ZAA rocket projectors were introduced in 1940 as simple weapons, which relied on the shotgun effect, using density of rocket fire against both low and higher flying targets. Their emplacements reflected variations in the size of ammunition (the two and three inch rockets) and the number and arrangement of barrels. The two inch rockets had a role comparable to the LAA guns against low level attack and dive bombing, while three inch rockets flew higher, and had a role similar to HAA fire against formations of bombers. Many ZAA sites were established on or adjacent to HAA sites or bombing decoys. At their most substantial, sites would have comprised a regular arrangement of projector emplacements and accompanying ammunition shelters, a manning hut for the radar crew, a fuse magazine (for ammunition assembly) and a command post. Their widespread layout was designed to minimise the danger to personnel and structures from the back blast of rockets. Over 50 ZAA batteries were built during World War II, a very small number of which have remains surviving. Any examples with surviving remains are considered to be of national importance.

The ZAA rocket battery 265m north east of Ashridge Farm is a particularly rare example with only one other of its type known to survive in Britain even though 50 ZAA battery sites are known to have been constructed in World War II. The battery, which retains at least 13 of its original rocket projector bases, provides a possibly unique association within England of an anti-aircraft rocket battery lying nearby to the remains of contemporary bombing decoy sites with one control building, although partly damaged, still standing and included within the monument. The monument acts as a reminder of the measures taken in World War II to protect, as far as possible, the citizens of Bristol from the worst effects of aerial bombardment by way of deceiving the enemy.


The monument includes an anti-aircraft rocket battery known as a ZAA battery, and the control building for a bombing decoy site. Both were constructed in the early years of World War II as part of the defences of the city of Bristol against German air raid attacks. The ZAA rocket battery and the control building are located in close proximity to one another at the western end of the Mendip Hills some 25km south west of the centre of Bristol. The ZAA rocket battery and control building were both part of a sophisticated system aimed at diverting hostile air attacks away from Bristol whilst at the same time drawing enemy bombers to within range of anti-aircraft fire. In the event of an imminent air raid on Bristol, lighting decoys were put into operation on Black Down, Burrington, to the north of the ZAA battery and in the vicinity of Ashridge Farm to the south of it. The lighting decoys, known as QL sites, attempted to simulate the city lights of Bristol under black-out conditions and they included devices to mimic the flickering lights of railway marshalling yards as seen from the air (the surviving decoy sites at Black Down are the subject of a separate scheduling). If the decoy was considered to have been successful in attracting aircraft then pre-prepared fires (known as Starfish or QF sites) were electrically ignited to create the illusion of targets having been set alight. The Starfish and QF sites were operated from control buildings placed at least 400m from the decoy fire. A QL decoy site at Ashridge Farm, was intended to replicate the position of the West Depot of Bristol's railway system when viewed from the air in relation to the Black Down decoy (known as Burrington C82) which provided other identifiable lighting patterns such as that for Temple Meads Station and Bristol's East Depot. The QL site at Ashridge Farm was backed up by a Starfish site although neither the QL nor the Starfish site survive; almost all decoy sites were systematically cleared at the end of the War. However, the control building for the Ashridge Farm decoy still stands adjacent to the ZAA battery to the north of the farm. It is of the standard design for a control building or bunker although it is missing its entrance wing walls and earth banking which have been stripped away in the early years of the 21st century. Comprising two rooms it is constructed of 0.35m thick brickwork with an outer blast-wall protecting the single entrance. The field control room, which is the room to the south, would have contained a stove, switchgear, and other communications equipment but of these internal features only the seating for the stove remains. The other room would have housed the power generators and three surviving concrete bases indicate their position; some galvanised ducting, probably for exhausts, survives attached to air vents in the walls. The control building operated as one of three which controlled the decoys, the other two being on Black Down, but unlike the others it is considered to have had a dual purpose in housing the operating circuits for the ZAA battery in addition to the circuitry for setting decoy lights and igniting decoy fires. The Z anti-aircraft rocket battery comprises 13 surviving octagonal rocket projector firing bases (from an original total of at least 19) together with the base of an ammunition store. The rocket bases appear, in a study made by Russett in 2002, to be arranged on a regular 42 foot (12.8m) grid although two pairs of bases on the extreme north of the array which no longer survive were much closer together than this. Of the thirteen rocket bases which are known to survive, five were present but buried below topsoil at the time of recording by Russett although their position has been plotted. The other eight were visible on the surface to varying degrees with two about 90% visible. Each of the rocket bases conforms to a standard design, this being an octagonal base of concrete about 2.6m in diameter with a 1.2m square concrete ramp on one side of the base and a flared concrete apron at the other. At the centre of the base within a ring about 1m in diameter are six equally spaced bolt fittings for holding the rocket projectors which were probably 3 inch (c.7.5cm) projectors for fire against formations of bombers. Around the perimeter of each base was either a cast iron protractor ring calibrated in degrees, or an incised ring made by pressing the concrete with the raised lettering of one of the cast iron rings. This arrangement would have allowed for the aiming of the rocket projectors. Within the rocket array is a concrete floor of what is considered to have been an ammunition store or fuse magazine. It has dimensions of 2m by 5.7m and its outer walls have been reduced to foundation level. Considerable information regarding the location, construction, and operation of World War II decoy sites and anti-aircraft batteries in the area of the Western Mendip Hills may be found in archives held by the Public Record Office. These archives have been subject to a national study by English Heritage. All barns and farm buildings and all fencing, gates, modern breeze-block walls and hardstandings are excluded from the scheduling, although the ground beneath all of these features 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.

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Books and journals
Dobinson, C, 'Twentieth Century Fortifications in England' in Bombing Decoys Of WWII, , Vol. Vol III, (1996)
Dobinson, C S, 'Twentieth Century Fortifications in England' in Anti-aircraft artillery, , Vol. Vol I, (1996)
Russett, V, 'Charterhouse Environs Research Team' in The Z battery site, Tynings Farm, Cheddar, (2002)
Schofield, A J, Webster, C J, Anderton, M J, 'Somerset Archaeology and Natural History' in Second World War Remains on Black Down: A Reinterpretation, (1999), 271-86
Schofield, A J, Webster, C J, Anderton, M J, 'Somerset Archaeology and Natural History' in Second World War Remains on Black Down: A Reinterpretation, (1999), 271-86
Held at NMRC, RAF, 3G/TUD/5332, (1946)


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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