World War II Bofors Anti-aircraft gun tower, Pickett-Hamilton fort and pillbox: part of the airfield defences of RAF West Malling fighter station


Heritage Category: Scheduled Monument

List Entry Number: 1020308

Date first listed: 07-Nov-2001


Ordnance survey map of World War II Bofors Anti-aircraft gun tower, Pickett-Hamilton fort and pillbox: part of the airfield defences of RAF West Malling fighter station
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The building or site itself may lie within the boundary of more than one authority.

County: Kent

District: Tonbridge and Malling (District Authority)

Parish: Kings Hill

National Grid Reference: TQ 67605 56259, TQ 68366 54940, TQ6794155698


Legacy Record - This information may be included in the List Entry Details.

Reasons for Designation

The importance of defending airfields against attack was realised before the outbreak of World War II and a strategy evolved as the war went on. Initially based on the principle of defence against air attack, anti-aircraft guns, air raid shelters and dispersed layouts, with fighter or `blast' pens to protect dispersed aircraft, are characteristics of this early phase. With time, however, the capture of the airfield became a more significant threat, and it was in this phase that the majority of surviving defence structures were constructed, mostly in the form of pillboxes and other types of machine gun post. The scale of airfield defence depended on the likelihood of attack, with those airfields in south or east England, and those close to navigable rivers, ports and dockyards being more heavily defended. But the types of structure used were fairly standard. For defence against air attack there were anti-aircraft gun positions, either small machine gun posts or more substantial towers for Bofors guns; air raid shelters were common, with many examples on each airfield; and for aircraft, widely dispersed to reduce the potential effects of attack, fighter pens were provided. These were groups together, usually in threes, and took the form of `E' shaped earthworks with shelter for ground crew. Night fighter stations also had sleep shelters where the crew could rest. For defence against capture, pillboxes were provided. These fortified gun positions took many forms, from standard ministry designs used throughout Britain and in all contexts, to designs specifically for airfield defence. Three Pickett-Hamilton forts were issued to many airfields and located on the flying field itself. Normally level with the ground, these forts were occupied by two persons who entered through the roof before raising the structure by a pneumatic mechanism to bring fire on the invading force. Other types of gun position include the Seagull trench, a complex linear defensive position, and rounded `Mushroom' pillboxes, while fighter pens were often protected by defended walls. Finally, airfield defence was co-ordinated from a Battle Headquarters, a heavily built structure of which under and above ground examples are known. Defences survive on a number of airfields, though few in anything like the original form or configuration, or with their Battle Headquarters. Examples are considered to be of particular importance where the defence provision is near complete, or where a portion of the airfield represents the nature of airfield defence that existed more widely across the site. Surviving structures will often be given coherence and context by surviving lengths of perimeter track and the concrete dispersal pads. In addition, some types of defence structure are rare survivals nationally, and all examples of Pickett- Hamilton forts, fighter pens and their associated sleep shelters, gun positions and Battle Headquarters closely associated with defence structures, are of national importance.

Despite the loss of parts of West Malling airfield to modern development, elements of its World War II defences survive well and represent a range of structures originally present. The Pickett-Hamilton fort is a well-preserved example of a rare form of gun emplacement, 242 of which were installed on 82 airfields in 1940-41 by a commercial construction company. The structure remains substantially unchanged and still retains all the principal elements of its original design, including its operating equipment. Its use in this location illustrates the often unique character of airfield structures, in this case specifically designed for the defence of the flying field. The anti-aircraft defences at West Malling are also notable for the survival of a Bofors Light Anti-aircraft gun tower at the north western corner of the former airfield, one of only three examples recorded on airfields nationally (the other two survive at Brooklands and Weston-super-Mare). As such, it is an important historic structure, serving as a physical record of similar emplacements which have been demolished elsewhere. The Type 24 irregular hexagonal pillbox is the most common form of pillbox built between 1939 and 1941. Pillboxes are especially representative of World War II defence structures and its association with the adjacent airfield adds to the significance of the structure. The pillbox, located on the southern side of West Malling airfield survives comparatively well. Its presence, as well as the strengthening of its walls in concrete, illustrates the perceived vulnerability of the airfield to attack by heavy German artillery. The importance of the surviving defence structures at West Malling is further enhanced by the overall significance of the airfield itself and the necessity to safeguard crucial elements in the defence of Britain against the threat of invasion during the greatest conflict of the 20th century.


Legacy Record - This information may be included in the List Entry Details.


The monument, which falls into three separate areas, includes a Bofors Light Anti-aircraft gun tower, a Pickett-Hamilton fort and a Type 24 pillbox. These structures formed part of the World War II defences of West Malling airfield, situated at Kings Hill, on top of the Greensand ridge, about 5km west of Maidstone. West Malling opened in 1930 as a private airfield for the Maidstone School of Flying, and was subsequently registered as Maidstone airport two years later. With the outbreak of World War II the airfield, which fell within Fighter Command's strategically important 11 Group (that part of Fighter Command covering the south east of England), was requisitioned by the RAF and soon re-opened as a front line fighter station in June 1940, and a satellite airfield to Biggin Hill, the principal fighter station in the area. A series of German bombing raids in August 1940 rendered the airfield unserviceable during the Battle of Britain, although it became a leading night fighter station the following year and played a key role in the 1944 campaign, code named Operation Diver, to defend the South East against the V1 flying bomb. With the end of the war West Malling became the main rehabilitation centre for prisoners of war returning from Germany. By this time its former grass runways, reinforced with Somerfield track (a heavy steel netting), had been replaced in concrete to meet the needs of the new jet aircraft. After the war the airfield was used for peacetime training, and during the 1960s the station was placed on `care and maintenance' by the RAF. The site was acquired by Kent County Council in 1970 and many of the airfield buildings are now used as offices by Tonbridge and Malling Borough Council. Since the 1990s, parts of the airfield have been lost to modern development. With the deepening threat of German invasion, the defence of Britain's airfields became a high priority during 1940. Fear of German `blitzkrieg' or `lightening' war tactics (involving rapid assault by air and seaborne troops, as witnessed in Europe in the Spring of 1940), led to the implementation of a national strategy for the defence of airfields in September 1940. West Malling was identified as one of 149 important airfields, located within 20 miles of vulnerable ports which could be targets for seaborne landings. Heavy defence of these airfields was therefore crucial to prevent capture of strategic landing grounds by enemy paratroops or gliderborne forces, rapidly followed by the arrival of transport aircraft carrying the principal invasion force. By the end of 1940, three Pickett-Hamilton forts had been installed at West Malling. These structures were designed in June 1940 by the New Kent Construction Company, specifically for the close defence of airfield runways. One of these forts was located towards the northern end of the flying field and survives next to what is now a modern access track. The structure consists of two, vertically sunken concrete cylinders, one mounted inside the other. The inner cylinder, known as the lifting head, remains in its lowered position, flush with the ground surface. The lifting head, pierced with three apertures for its main Vickers or Bren gun, was designed to be raised to its firing position by means of a pneumatic jack, supplemented by a manual pump for emergency use. The fort retains most of its original features, including its internal operating equipment as well as the access hatch in the lid of the lifting head through which the crew of two men entered at ground level. The second fort was removed from the airfield in 1983, and survives on display at the Imperial War Museum, Duxford. The location of the third fort has not yet been identified. Adjacent to the southern perimeter track at West Malling is a Type 24 hexagonal pillbox which originally formed part of an inner and outer series of about 20-30 pillboxes. The small squat structure measures about 6m by 5.5m and is entered through a doorway on its longer eastern side. The entrance is protected by a low externally attached brick wall, and is flanked by one of two loopholes, the second of which is located in the opposite wall of the pillbox. In accordance with orders issued in 1941, the walls of the original brick built structure were thickened by the external application of reinforced concrete, and evidence suggests that at least two additional loopholes were also blocked at this time. These measures were intended to strengthen pillboxes at vulnerable locations against heavy German artillery. The presence of a recess in the edge of the roof above each opening suggests that further protection for the gun crew may have been provided in the form of shields, designed to deflect flame-throwers. A rare surviving example of a Bofors Light Anti-aircraft gun tower also survives close to a modern roundabout, at the north western approach to the airfield. The concrete and brick built tower appears to conform to type `DFW 55087', which was designed at the end of 1939, with the earliest examples constructed during the first half of 1940. The tower was designed to raise a 40mm Bofors gun and its operational equipment, above surrounding obstacles in order to achieve an all-round field of fire in defending the airfield from attack by fast moving, low flying enemy aircraft. The tower stands to a height of about 20m and consists of two parallel, independent structures, separated for much of their height by a 1m gap and linked at intervals by cantilevered concrete bridges to allow movement between the towers. At ground level, the gap functioned as a passageway, providing access to the chambers on either side. The combined structure measures 9m from north to south by 4m east to west and each tower was constructed on four levels: three internal levels contained the magazine and accommodation chambers, lit by vertical two-light windows. The emplacement was located on the flat concrete roof, which projects beyond the brick walls of the tower and was reached via a ladder from the chamber below. The ordnance was centrally mounted on the roof of the northern tower and was served by ammunition lockers at each corner of the roof space. The roof of the southern tower supported the target predictor and was separated from the gun platform by a narrow intervening gap, above the passage below, to insulate this sensitive equipment from the vibration of the Bofors gun. Several temporary station buildings survive around the airfield perimeter. These derelict structures include externally rendered, temporary brick buildings, dispersed from the main technical site in anticipation of concentrated bombing raids. These structures are not included in the current scheduling. Among the more architecturally sophisticated airfield buildings, the Neo-Georgian style Officers' Mess is Listed Grade II. Several semi-sunken Stanton air raid shelters survive, in buried form, near the barrack buildings. These are infilled and are not therefore included in the scheduling. Other structures associated with the defence of the airfield, such as the battle headquarters and the protected aircraft dispersal pens, were destroyed towards the end of the 20th century, although further, as yet unidentified elements may survive beyond the area of the monument. All modern fixtures and fittings associated with the Bofors tower, including modern doors and window boxes, and all modern materials and equipment stored within the tower are excluded from the scheduling; the ground beneath these features, or the structures to which they are attached, however, is included.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


The contents of this record have been generated from a legacy data system.

Legacy System number: 34304

Legacy System: RSM


Books and journals
Barrymore Halpenny, B, Action stations 8: Military airfields of Greater London, (1984)
Brooks, R J, From Moths to Merlins: the story of West Malling airfield, (1987)
Dobinson, C S, Twentieth Century Fortifications in England: Anti-aircraft defences, (1996)
Dobinson, C S, Twentieth Century Fortifications in England: Anti-aircraft artillery, 1914-46, (1996)
Dobinson, C S, Twentieth Century Fortifications in England: Volume X Airfield Defences in WWII, (2000)

End of official listing