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Hunsdon World War II airfield defences

A Scheduled Monument in Hunsdon, Hertfordshire

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Latitude: 51.8108 / 51°48'38"N

Longitude: 0.0681 / 0°4'5"E

OS Eastings: 542666.1987

OS Northings: 214488.4057

OS Grid: TL426144

Mapcode National: GBR LD2.D1B

Mapcode Global: VHHM0.4RC5

Entry Name: Hunsdon World War II airfield defences

Scheduled Date: 17 October 2002

Source: Historic England

Source ID: 1020748

English Heritage Legacy ID: 32450

County: Hertfordshire

Civil Parish: Hunsdon

Built-Up Area: Hunsdon

Traditional County: Hertfordshire

Lieutenancy Area (Ceremonial County): Hertfordshire

Church of England Parish: Hunsdon

Church of England Diocese: St.Albans


The monument, which is in 14 separate areas of protection, includes the
perimeter defences and associated structures of the former World War II
fighter defence station known as RAF Hunsdon. All of these remains are located
on or close to the perimeter of the now disused airfield lying to the east and
south east of Hunsdon village.

In 1939 the Air Ministry requisitioned an area of agricultural land adjacent
to Hunsdon village. On the 9th October 1940 construction work began on the
site and it opened in February 1941. The new fighter station had two
intersecting runways (the longest some 1750 yards or 1600m ENE-WSW), a
perimeter road and a whole range of brick, wooden, prefabricated and steel
buildings and structures including squadron headquarters, dispersed
sleeping and messing accommodation, fighter pens and hangars and airfield
defence structures. The majority of the pillboxes and associated
structures built to defend the airfield from both air and ground attack
still survive. These are described below in relation to the 14 separate
areas of protection, each enclosing a structure or group of associated

The first area of protection encloses a large brick and concrete hexagonal
pillbox sited adjacent to the B180 road guarding the southern approaches to
the village some 300m to the west of the airfield perimeter road. The pillbox
has a diameter of 7.5m and the walls are some 1.5m thick. Each gun aperture
(six in all) measures 0.25 sq m at its interior wall expanding through a
series of small steps to an opening 1.4m by 0.9m in the exterior face. Two
Turnbull machine-gun mounting pivots are extant in one of the loopholes; these
would have allowed a steel cradle, housing the machine gun, to be hung in
the aperture.

The second area encloses a hexagonal pillbox in the garden of Hunsdon Lodge
Farm, Drury Lane. Small (diameter 4.7m) and built with comparatively thin
brick walls, non-flaring gun apertures (without Turnbull mountings) and a
full-height doorway it may have served as an communications post.

The third and fourth areas enclose the next two pillboxes on or near to
the northern circuit of the airfield perimeter road, one located some 30m to
the west of the Old Hunsdon Lodge Farm buildings and the second some 60m to
the south west. These are both typical Hunsdon pillboxes of hexagonal shape
and massive dimensions (diameter 7.5m, wall thickness 1.75m). Turnbull
mountings at some of the loopholes provide evidence for the level of armament.

Both pillboxes are accessed via low L-shaped tunnel entrances, partly lined
with anti-ricochet brickwork. Their maximum internal diameter is 4m and each
incorporates a central Y-shaped anti-ricochet brick wall.

The fifth area encloses a cantilever type pillbox. These were designed
specifically for airfield defence by FC Construction Company Ltd and take the
form of a circular brick-lined pit (1.5m deep by 5.5m diameter) in the centre
of which is a 2m high pillar surmounted by a concrete dish (of the same
diameter as the pit); the gap between the top of the pit and bottom of the
concrete dish affords a 360 degree firing capability to the occupants of the
cantilever type pillbox.

The sixth area encloses an air raid shelter some 30m to the west of the
pillbox. It is of Stanton type, formed from precast concrete parabolic
panels bolted together to form a vaulted shelter some 9.1m in length and
2.3m wide at its base. It would have been covered in earth during wartime
as extra protection, with its escape hatch protruding through the top of
the mound.

The eighth and ninth areas both lie within Black Hut Wood. Each area encloses
a pillbox with its associated trenches and ammunition store. On the west
corner of Black Hut Wood the eighth area has at its centre a massive Hunsdon
type pillbox of the same construction as those described in areas three and
four. Approximately 30m from the pillbox two brick-lined trenches form a
V-shape around the north east quarter of the field of fire from the
pillbox. One trench is straight, the other is zig-zag; both are
some 21m long by 1m wide with built-in ammunition recesses along their
length. An auxiliary brick-built semi-sunken structure 50m to the
south east is an ammunition store listed as `Ammunition Store 20mm' on an
Air Ministry plan of the airfield dated June 1946. The store is
approximately 3.7m long by 2.8m wide lit by three small windows. In one
internal corner of the room iron rungs lead up to what was once an escape
hatch in the roof.

On the eastern edge of the wood is a similar arrangement of pillbox, trenches
and ammunition store; these are enclosed within the ninth and tenth areas.
The pillbox is of the same massive dimensions as that at the other end of
the wood. The associated trenches are infilled but their course can be
traced in the ground as a series of depressions. The associated ammunition
store lies to the north east in the tenth separate area of protection.
It is brick built at ground level and has the same dimensions as that
to the west. It too has a ladder in one corner leading to an escape hatch.

Along the southern perimeter, within a small triangular-shaped wood known as
Tuck's Spring, two sleeping shelters lie within the eleventh area. The
easternmost shelter measures 6.5m by 3.5m with porches or blast walls at each
end; the roof is flat and there are no windows. The westernmost shelter is of
the same design but longer, measuring 13m in length, and has only one porch at
its northern end. The buildings are divided into bays by internal cross-walls,
each bay housing up to six bunk beds (the steel supports for these are still
affixed to the wall). Ventilation is afforded by air bricks (regularly spaced
low down in the walls) and by an air extractor system (the ducting remains in
place running continually along the ceilings of each building). Power cables
and light fittings are still in place in both shelters. An annotated plan of
the airfield produced by the Air Ministry in June 1946 labels these buildings
as sleeping shelters for 18 and 33 personnel. Their purpose was to provide
overnight accommodation in the event of air raids.

The twelfth area includes a brick-built hexagonal pillbox with a concrete
roof located at the eastern tip of Tuck's Spring. Basically a Type 22
design, its relatively thin walls render it bullet-proof but not
shell-proof. It has six gun apertures in its exterior wall (one in each of
its faces) and a brick-built tunnel entrance at its northern side.
To the south west is the Battle Headquarters from where the airfield's
defences would be directed during an air attack or ground invasion.

The thirteenth area encloses the Battle Headquarters building and the trenches
surrounding it. The building is mostly underground: a Type 11008/41 design
which replaced above ground battle headquarters during the course of the
war after the latter proved vulnerable to air attack. It has three
subterranean rooms (sleeping quarters, office and toilet) and at its
western end one partly above ground observation tower. The structure has
impressive defences: extending in a semi-circle around its eastern side
are brick-built trenches with integral shelters leading to one entrance at
the eastern end of the building. The structure has another entrance next
to the observation tower: a narrow rectangular opening (which would
originally have had a steel hatch) gives access to the observation tower
via an iron ladder. The observation tower has a viewing slit all the way
round; formed by the presence of iron spacers supporting a massive
concrete roof. The subterranean part of the building is still partly
earth-covered. The Battle Headquarters is a very formidable structure
which would have been almost impregnable under attack.

The fourteenth and seventh areas enclose two further concrete pillboxes
east of Acorn Street: one (the fourteenth area) is in a field
approximately 15m from the airfield perimeter road; the seventh is
immediately adjacent to the road. Both pillboxes are of the massive
typically Hunsdon type seen elsewhere around the perimeter and exhibit the
brick shuttering characteristic of the other pillboxes of this type. The
pillbox immediately adjacent to Acorn Street has loophole apertures in
each of its six wall faces but no facility for mounting machine guns. In
contrast the pillbox in the field does have Turnbull machine gun mounting
pivots built into two of its apertures.

The history of Hunsdon airfield is well documented. The first operational
unit was No 85 Squadron which operated Hurricanes, but it was the
Mosquitos of Nos 464 (RAAF), 487 (RNZAF) and 21 Squadrons which achieved
fame with the Amiens Prison raid in February 1944 (`Operation Jericho').
Mosquito night-fighters and Mustangs were deployed from the base until
July 1947 when the airfield finally closed.

All modern fencelines and structures associated with the activities of
paintballers in Black Hut Wood are excluded from the scheduling, although
the ground beneath them and the structures to which they are attached is

The site of the monument is shown on the attached map extract.

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.

Defences survive on a number of airfields, though few retain their original
form or configuration and even fewer retain the nerve centre of the defences,
the Battle Headquarters. The perimeter defences at Hunsdon airfield retain
much of their original configuration and also their Battle Headquarters.

The perimeter defence structures at Hunsdon survive exceptionally well with
ten of the fifteen original pillboxes still extant. These include a cantilever
pillbox; an innovative design for a pillbox by FC Construction Ltd. Designed
specifically for airfield defence, only a few now survive around the
country. The other surviving nine pillboxes are of Type 22 hexagonal
design but with some modifications. In particular the massive size of
seven of the Hunsdon pillboxes (over 7m in diameter with walls 1.75m
thick) is unparalleled in this country and makes them of particular interest.

In addition to the pillboxes the associated structures at Hunsdon are rare
survivals: the air raid shelter, sleeping shelters and the ammunition
stores. In particular the two sleeping shelters in Tuck's Spring are very
rare nationally with only six known examples. Taken individually
therefore several of the Hunsdon airfield defence structures can be seen
as of national significance; however, it is the survival of the entire
group with a distribution around the whole of the airfield perimeter road
which provides such a graphic illustration of the nature of airfield
defence during World War II.

Source: Historic England


Books and journals
Dobinson, C S, Twentieth Century Fortifications in England: Volume X Airfield Defences in WWII, (2000), 79
Dobinson, C S, Twentieth Century Fortifications in England: Volume X Airfield Defences in WWII, (2000), 79
Hitching, F, V, , The Royal Air Force at Hunsdon 1941-1945, (1990)
Hitching, F, V, , The Royal Air Force at Hunsdon 1941-1945, (1990)
Hitching, F, V, , The Royal Air Force at Hunsdon 1941-1945, (1990)
Hitching, F, V, , The Royal Air Force at Hunsdon 1941-1945, (1990)
3 April, RAF, 106G UK 1367 Frames 5165, 7,8, (1946)
3 April, RAF, 106G UK 1367 Frames 5165,6,7, (1946)
3 April, RAF, 106G UK1367 Frame 5165, (1946)
3 April, RAF, 106G UK1367 Frames 5165, 6, 7, (1946)
7 June, RAF, 106G 1565 Frame 3177, (1946)
7 June, RAF, 106G UK 1565 Frame 3177, (1946)
7 June, RAF, 106G UK1565 Frame 3177, (1946)
7 June, RAF, 106G UK1565 Frame 3177, (1946)
In Herts. SMR, Savills, FPD, Photographic Record of Sites at Hunsdon Airfield, (1997)
In Herts. SMR, Savills, FPD, Photographic Record of Sites at Hunsdon Airfield, (1997)
In Herts. SMR, Savills, FPD, Photographic Record of Sites at Hunsdon Airfield, (1997)
In Herts. SMR, Savills, FPD, Photographic Record of Sites at Hunsdon Airfield, (1997)
In Herts. SMR, Savills, FPD, Photographic Record of Sites at Hunsdon Airfield, (1997)
In Herts. SMR, Savills, FPD, Photographic Record of Sites at Hunsdon Airfield, (1997)
RAF, 106G UK1367 Frames 5165, 6, 7, (1946)
Report in Herts. SMR, Nash, F, Ammunition Store, Hunsdon Airfield, (2001)
Thompson, GR, Report on Hunsdon Airfield Structures, (1997)
Thompson, GR, Report on Hunsdon Airfield Structures, (1997)
Thompson, GR, Report on Hunsdon Airfield Structures, (1997)
Title: Plan of Hunsdon Airfield
Source Date: 1946
At RAF Hendon Museum
Title: Plan of Hunsdon Airfield
Source Date: 1946
RAF Hendon Museum

Source: Historic England

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