Details

The monument, which is in three separate areas of protection, includes three
Pickett-Hamilton forts which were installed in late 1940 as part of the ground
defences on Swanton Morley airfield.

Swanton Morley airfield was designed as a medium bomber station with a grass
strip flying field, and opened in September 1940 as a full station within No.2
Group of Bomber Command. In the first year of operation it was a base for
squadrons flying Blenheims and was also used by Spitfires of 152 Squadron. It
was also the airfield where the de Havilland Mosquito first entered service.
In late 1941 it received No.226 Squadron, equipped first with Douglas Boston
IIIs and then, from 1943, with Mitchells. In June 1942 it was the scene of the
launch of the first combined British-American bombing raid, at which both
Churchill and Eisenhower were present. Swanton Morley remained in use as an
RAF station until 1995 and the grass flying field was used for glider
training.

Pickett-Hamilton forts were designed specifically for airfield defence on the
flying field and are a form of retractable pill box, the upper section of
which could be lowered flush with the ground surface when not in use, so as
not to obstruct aircraft landing or taking off. Each consisted of two hollow,
concentric pre-cast concrete drums resting on a concrete base. The outer drum
and base, measuring approximately 2.5m in depth were sunk into the ground. The
inner drum, pierced by three rifle loopholes, formed the lifting head and was
designed to be raised approximately 0.75m by means of a central jack, using a
compressed air bottle or hand pump, although this system proved unreliable and
was later supplemented by oil pumps. When the lifting head was in the lowered
position an external flange rested on the upper section of the outer drum,
which incorporated a pre-cast surround or collar. Access was by means of a
metal hatch in the roof of the lifting head and metal rungs set into the inner
face. The interior fittings included a free standing circular firing step
around the central column, a small electric light, and a telephone for
communication with the airfield battle headquarters.

The concrete tops of the lifting heads of the three Pickett-Hamilton forts at
Swanton Morley are partly overgrown but visible, with the metal hatches set
off centre. If fully exposed they would be around 2m in diameter, with the
upper sections of the outer drums extending about 0.3m beyond, giving an
overall diameter of 2.6m. They are located on the flying field to the north
west of the line of the main runway, which is visible on aerial photographs
taken by the RAF in 1946 and is still marked by concrete pads for lights. It
was aligned north east-south west, with subsidiary runways running north
west-south east and WNW-ESE. The southernmost of the three forts is located
approximately 720m WSW of a triangulation pillar and 80m from the line of the
runway. The access hatch is secured by a bar across it, but the lifting
mechanism is recorded as intact, though rusted. The second lies some 250m to
the NNE of this, about 140m from the line of the main runway and within the
triangle which this formed with the two subsidiary runways. The interior is
completely flooded but is thought to contain original features. The third is
located in the north eastern part of the flying field, about 254m north east
of the second and 20m from the line of the main runway. This has been partly
infilled, but the top of the column of the jack remains visible.

The bar which has been installed to secure the hatch of the first
Pickett-Hamilton fort is excluded from the scheduling although the hatch
itself is included.

MAP EXTRACT
The site of the monument is shown on the attached map extract.
It includes a 1 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
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.

The three Pickett-Hamilton forts at Swanton Morley airfield are of importance
as comparatively rare examples of an unusual and innovative type of airfield
defence installation. The outer structure and lifting heads of all three
remain intact and they are known or believed to retain internal features,
including parts of the hydraulic mechanism.

Source: Historic England

Sources

Books and journals
Dobinson, C S, Twentieth Century Fortifications in England, (2000), 58,60
Dobinson, C S, Twentieth Century Fortifications in England, (2000), 58,60
Dobinson, C S, Twentieth Century Fortifications in England, (2000), 58, 60
Other
Norfolk: 2830, (1994)

Source: Historic England