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

A Scheduled Monument in Kings Hill, Kent

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Latitude: 51.2808 / 51°16'50"N

Longitude: 0.4018 / 0°24'6"E

OS Eastings: 567605.3032

OS Northings: 156259.2658

OS Grid: TQ676562

Mapcode National: GBR NPK.LFG

Mapcode Global: VHJMB.X29G

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

Scheduled Date: 7 November 2001

Source: Historic England

Source ID: 1020308

English Heritage Legacy ID: 34304

County: Kent

Civil Parish: Kings Hill

Built-Up Area: King's Hill

Traditional County: Kent

Lieutenancy Area (Ceremonial County): Kent

Church of England Parish: West Malling St Mary

Church of England Diocese: Rochester


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
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.

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.

Source: Historic England

Reasons for Scheduling

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
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.

Source: Historic England


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)

Source: Historic England

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