Group of four World War II fighter pens at the former airfield of RAF Kenley


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:


Ordnance survey map of Group of four World War II fighter pens at the former airfield of RAF Kenley
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The building or site itself may lie within the boundary of more than one authority.

Greater London Authority
Croydon (London Borough)
National Grid Reference:
TQ 32324 57955, TQ 32499 58117, TQ 32636 58151, TQ 32741 58237

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.

Although Kenley no longer has the pillboxes and other elements of an airfield defence surviving, it is the only example identified through a national survey to retain nearly all of its dispersed fighter pens. As such, and in association with its historical significance, it is a nationally important monument which demonstrates both planned defence of aircraft from attack while on the ground and the success of this policy as so few aircraft were lost on the ground despite repeated and heavy aerial attack.


The monument, which falls into four separate areas of protection, includes part of the former World War II fighter station known as RAF Kenley. These four fighter pens were part of a group, originally numbering twelve, dispersed around the runway perimeter track of the airfield; the other seven surviving pens being the subject of a separate scheduling. During World War II fighter aircraft were considered to be very vulnerable when on the ground either from air attack, or, during the early years of the War, from possible ground attack, and elaborate precautions were taken to prevent any loss of, or damage to, aircraft when not in action. As a result, fighter aircraft were often held in dispersed pens located around the perimeter of the airfields but with easy access to the main runways. These pens were often constructed in an E-shape with two bays, one for each aircraft. At Kenley 11 of the original 12 pens survive, originally providing protection for up to 24 aircraft at a time. Kenley was first used as a Royal Flying Corps aerodrome in 1917 although the buildings associated with the grass flying field have all now gone. An Act of Parliament in 1939, following agreement to provide all-weather runways and perimeter tracks for critical fighter stations, led to the expansion and rebuilding of RAF Kenley to provide two 800 yard (732m) runways which were completed in December 1939. By April 1940 all 12 fighter pens had also been completed and the Station was fully operational. The aircraft based at Kenley formed part of 11 Group and it was able to house two squadrons of twelve aircraft each in the fighter pens and a further squadron dispersed on open hard standings. Kenley was subjected to some of the most sustained attacks on fighter stations by the Luftwaffe in 1940. On 18th August one raid led to the loss of three personnel, three hangers and two aircraft; photographs of an attack on a fighter pen appeared in the German Der Adler magazine. On 30th August 39 personnel were killed and 26 wounded and on the following day the operations block was damaged. Despite these sustained raids Kenley continued to launch fighter aircraft and played a vital role throughout the Battle of Britain and the later Blitz of London. Its runway was extended by a further 200 yards (183m) in 1943 to allow larger aircraft to land. The four standard Fighter Command Works aircraft fighter pens within this scheduling were built to the north of the all-weather perimeter track on the northern side of the airfield. They consist of an approximately 50m long external axis bank which is up to 6.5m wide. To the inner (southern side) of this lie two similar but shorter banks measuring 22.5m long with the internal space left open towards the perimeter track and divided by a central blast bank which leaves two roughly equal bays measuring approximately 16.5 sq m. This standard format provided some degree of protection to aircraft in the open while allowing rapid deployment to the runways as required. This standard layout of a twin fighter pen with brick or concrete dwarf retaining walls and earthwork traverses which protected three sides of, and separated, two bays, each for one aircraft, was designed and trialled in August 1938 and was the preferred type of Sir Hugh Dowding, who was instrumental in the planning of all weather fighter stations. At the rear of each pen is a precast concrete Stanton type air-raid shelter for up to 25 men with access from either bay. Each pen faces onto a concrete apron, providing access to the perimeter track and turning space. These vary in layout to break up the symmetry of the ground plan when viewed from above. Further supporting defensive elements including ancillary buildings, pillboxes and other structures no longer exist at Kenley. All modern fences, gates, and all post-August 1946 ground surfaces 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.

Legacy System number:
Legacy System:


Books and journals
Flint, P, RAF Kenley: The Story of the Royal Airforce Station 1917-1974, (1985)
1:500 Plan, Croydon, B C, Kenley Airfield, (2001)
PRO station record book, AIR 28/419, Operations Record Book, (1939)
See 146456,
See 146456, Operations Record Book,


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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