Hunsdon World War II airfield defences


Heritage Category: Scheduled Monument

List Entry Number: 1020748

Date first listed: 17-Oct-2002


Ordnance survey map of Hunsdon World War II airfield defences
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The building or site itself may lie within the boundary of more than one authority.

County: Hertfordshire

District: East Hertfordshire (District Authority)

Parish: Eastwick

County: Hertfordshire

District: East Hertfordshire (District Authority)

Parish: Hunsdon

National Grid Reference: TL 41721 13403, TL 41870 13523, TL 42336 14386, TL 42351 14252, TL 42474 14218, TL 42512 14218, TL 42522 13272, TL 42667 14482, TL 42809 13515, TL 42819 13387, TL 42932 14378, TL 42975 14429, TL4159713870, TL4202214232


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.

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.


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


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 structures.

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 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: 32450

Legacy System: RSM


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 Author: Publisher: Surveyor: At RAF Hendon Museum
Title: Plan of Hunsdon Airfield Source Date: 1946 Author: Publisher: Surveyor: RAF Hendon Museum

End of official listing