Bunker, RAF Daws Hill

Bunker, RAF Daws Hill

This is a reinforced concrete bunker designed to withstand the shock of nearby explosions. The structure comprises an outer shell with 6-foot (1.83 metre) thick external walls, with an inner wall separated from the outer wall by a 10-foot (3 metre) wide full-height void that wraps around the entire perimeter. The bunker was dug into a sloping site to make optimal use of the topography.

The bunker is lined internally in steel plates, probably added during 1980s enhancements. It is rectangular on plan and provides 23,000 square feet (2,136.7 square metres) of floor space across three levels.

The bunker's position on the surface is marked by four large cuboid vents approximately 4 metres tall, clad in steel plate about 2.5 centimetres thick and built on concrete bases. Three vents are positioned in a line along the south side, with two lying either side of the building and one sited close to the western perimeter fence and another in the north-west corner of the compound. The upper three vents expelled air; the lower vent was likely the air intake.

Access is gained from a sloping track leading down to the building and a flight of external steps to an external guardroom. The main entrance to the bunker is through a caged entrance to the south with thick steel blast doors, from which internal stairs lead to the lowest level accessed through a single steel door. A second caged entrance north of the guardroom leads to heavy blast doors containing the 1980s decontamination cell. An emergency exit from Level 3 opens onto stairs which emerge at higher level to the south-west of the main entrance.

The full-height void contains sewage systems, effluent tanks, non-potable water tanks, fans, compressors, filters and ventilation shafts. The outer walls and some inner walls and roofs are reinforced with steel plates, probably to provide enhanced protection in the event of nuclear explosion. Sections are separated by heavy steel doors. Above Level 1, the void is fitted with additional service plant.

All three levels are organised around the same basic plan of three long rectangular compartments defined by longitudinal concrete walls. Rooms typically have concrete floors and most have suspended ceilings. Doors are secured by combination locks, and some retain original numbers and acronyms relating to their function.

The bottom level (Level 1) is divided into 23 rooms of varying sizes, most appearing to have housed computer equipment. A number of rooms contain halon gas fire suppressant systems.

The middle floor (Level 2) is divided into 14 rooms, with a proportion given over to air conditioning plant. In room 2/2, two wartime support columns are visible. Above the suspended ceiling is a steel plate that may have been used to create a Faraday cage to prevent the escape of electronic emissions, or to protect equipment from the effects of electro-magnetic pulse (EMP), one of the effects of nuclear explosion. The plate may also represent the infilling of the wartime map well. The wartime map room and tote board were housed on this floor.

The top floor (Level 3) is divided into 8 large rooms, with the central room 3/1 subdivided into two. Rooms 3/1 and 3/2 are fitted with halon gas fire suppressant systems; 3/2 has heavy-duty cabling suspended from the ceiling; 3/1 contains a sign noting 'You are leaving a SCIF' (Special Communication Intelligence Facility). The power intake from the Generator House fed into rooms 3/5 and 3/6, which contain filter equipment. From this level, an emergency exit leads to stairs to the south-west of the main entrance which lead to a caged entrance. To either side of the stair are rails for a winch system used to install heavy equipment, operated from a control box to the south of the lift entrance. At the bottom level an overhead crane was used to move equipment into the bunker; a hydraulically operated steel floor panel gave access to the lower levels.

All fittings and equipment have been removed from the main rooms and no wartime fittings remain in place.

The 1980s decontamination cell is accessed through steel blast doors at the outer entrance, leading into a series of small interlocking rooms fitted with stainless steel fittings. Personnel passed from the entrance through compartments containing bins for disposal of contaminated clothing and equipment before showering and changing into fresh clothes. The cell was controlled by a central console and fittings appear to be intact with original signage in place. A further set of steel blast doors opens into the bunker.