Details

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.

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
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.

Source: Historic England

Sources

Books and journals
Flint, P, RAF Kenley: The Story of the Royal Airforce Station 1917-1974, (1985)
Other
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,

Source: Historic England