A former World War II military bunker constructed in 1942 and adapted in the 1980s with the additions of vents and a decontamination unit.
Reason for Listing
The underground bunker, constructed 1942, including the four attached 1980s external vents and decontamination unit, formerly within RAF Daws Hill and now within the grounds of Wycombe Abbey School, is listed at Grade II* for the following principal reasons:
* Structural interest: one of the largest purpose-built WWII British bunkers, of unique form in a British context, comprising a double-skinned subterranean cuboid structure built into the side of a hill, formed of an inner bunker laid out on three levels contained by a full-height void and outer bunker skin;
* Historic interest: high-level US headquarters serving as the nerve-centre of United States Army Air Force European bombing campaign in WWII, refurbished as the main command centre of United States Air Force 7th Air Division in the 1950s and as the United States European Command wartime headquarters in the 1980s;
* Intactness: WWII structure, retaining evidence of its continued use and adaptation during the Cold War in response to military strategy and particularly to increasing military threat over five decades;
* Supplementary protection: in line with Nato policy, subsequently hardened against nuclear, biological and chemical warfare, creating a Faraday cage; exceptionally intact and resonant Cold War decontamination unit.
This account draws on the report by English Heritage, Heritage Protection and Planning Assessment Team (RAF Daws Hill, Buckinghamshire, 16 April 2012) where the site is described in greater depth. For consistency, building identification numbers follow those in that report. The map depictions of the bunker and vents are approximate.
The bunker lies within a secure compound adjacent to the former RAF Daws Hill. It is reached by a track which was formerly one of the woodland rides within Wycombe Abbey Park. Within the compound there is a contemporary stand-by generator , a large US store constructed in the 1980s , two prefabricated US office buildings [1701, 1705], a guard post at the entrance to the bunker , a guard post at the entrance to the compound , an emergency water supply  and an electricity sub-station. The compound is enclosed by an outer wooden fence and inner wire mesh and barbed wire fence. Attached to the wire fence and at the entrance are movement sensors and lights. The main entrance is controlled by a lifting barrier and two sets of gates at either end of a vehicle pull-in and inspection area. Adjacent to it is a lattice column probably for a surveillance camera (removed). Apart from the stand-by generator (NHLE 1411420), these other buildings and structures are not included in the listing.
HISTORY OF THE SITE
During WWII a three-storey underground command headquarters, codenamed PINETREE, was established in the grounds of Wycombe Abbey School which had been requisitioned by the Air Ministry in 1942. The park had been laid out in the mid- to late-C18 by Lancelot ‘Capability’ Brown and ‘improved’ later in the century by Humphry Repton. The mansion, now Wycombe Abbey School, was remodelled c1803-4 by James Wyatt and extended in the late C19 (listed Grade II*). It may lie on the site of a medieval hospital.
Initially it appears that the command headquarters was jointly occupied by the RAF and United States Army Air Force (USAAF) before it became the main headquarters of USAAF’S Eighth Air Force. From it the USAAF's daylight offensive strategic bombing campaign of Europe was planned and coordinated.
In response to heightened tension between the Soviet Union and the West in the late 1940s and the outbreak of the Korean War in 1950, US forces and their nuclear armed bombers, and later in the 1950s missiles, were deployed across Europe. The bunker was refurbished in the mid-1950s for the United States Strategic Air Command 7th Air Division as its main European planning and operations centre responsible for organising nuclear attacks against the Soviet Union. Had war broken out, it would have been from High Wycombe that the command to launch a strike would have been given. It continued as a command centre for US forces after the renewal of a fully co-ordinated strike plan between the UK and US in 1958, for example during the Cuban Missile Crisis in 1962.
From c1970-1981 the bunker was unoccupied. Chosen as the US European Command’s (USECOM) headquarters in the event of war, in 1983 it was again refurbished in line with the policy of Flexible Response, to harden it against nuclear, biological, and chemical attack and the effects of electro magnetic pulse (EMP) released by a nuclear detonation. Huge amounts of money were spent on upgrading the site and installing complex computer systems. The decontamination cell was added, a message relay system was installed in the bunker and new surface buildings were added to the compound. As part of the Joint Strategic Targetting Group during the early 1980s, Daws Hill was one of three centres in Europe responsible for planning cruise missile operations.
Aside from the bunker, the most significant building on the site is the emergency power plant, north of the main entrance to the compound, and probably constructed in the 1980s. Functionally it was an integral and essential component of the 1980s bunker but because of the bunker's prior existence it was built as a separate structure. It is a partly-buried reinforced concrete structure where the rear wall and walls of the smaller rooms were reinforced internally in steel plates, providing enhanced protection against nuclear explosion. The north-facing entrance has two pairs of double steel doors which were wide enough to permit the installation of the plant’s diesel generators, now removed. To the east are separate rooms which housed the plant’s switchgear, which remain intact. Above are two vents that may represent an air inlet and exhaust outlet. There are no decontamination facilities here.
As a consequence of the Intermediate Nuclear Forces Treaty (1987) and the end of Cold War, the bunker became superfluous to operational use. It closed in 1991 and was de-activated in 1993 and has since been unused.
The bunker is of reinforced concrete, lined internally in steel plates, probably during the 1980s enhancement; vents clad steel plate on a concrete base.
PLAN AND STRUCTURE
The bunker is rectangular on plan, and was designed to absorb the shock of a nearby explosion. It comprises an outer shell with 6ft (1.83m) thick external walls. The inner wall of the bunker is separated from the outer wall by a 10ft (3m) wide full height void which wraps round the perimeter of the structure.
The bunker is laid out on three levels, Level 1 being the lowest, and in total provides 23,000 sq ft (2136.7 sq m) of floor space. To make optimal use of the topography, the bunker was dug into the side of the slope. On the surface the bunker’s position is betrayed by four large vents, three in a line marking its south side; two lie either side of the building, one is sited close to the western perimeter fence and the fourth is in the north-west corner of the compound. The vents are massive cuboid structures c4m tall and clad in steel plate c2.5 cm thick and built on concrete bases. The upper three vents are likely to have expelled air; the lower vent, set on a base, is likely to have been the air intake.
The bunker is accessed from a track that slopes down to the building and down a flight of external steps to an external guardroom. During normal operations the bunker was entered through a caged entrance to the south of this guard post, through thick steel blast doors from which a flight of internal stairs leads to the bottom level of the bunker entered through a single steel door and from where doors give access to the void and to the bunker. North of the guard room a second caged entrance leads to heavy blast doors containing the 1980s decontamination cell. There is also an emergency exit from Level 3. It opens on to stairs which emerge at higher level to the south-west of the main entrance.
The void is full height. Outer walls and some inner walls and roofs are reinforced with steel plates, probably to provide enhanced protection in the event of a nuclear explosion. Sections are separated by heavy steel doors. Progressing clockwise it houses sewage systems, effluent tanks, non-potable water tanks, fans and compressors. The western side is taken up with filters and above the northern side are the ventilation shafts. The eastern section is almost empty except for a transformer at its southern end. Above Level 1 the void is fitted with additional service plant. Pursuant to s.1 (5A) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (‘the Act’) it is declared that all of the plant within the void is not of special architectural or historic interest.
All three levels are organised around the same basic plan of three long rectangular compartments defined by longitudinal concrete walls. Typically rooms have concrete floors. Most have suspended ceilings. Openings within them vary from level to level and internal partitions relate to the bunker’s latest use. Doors are secured by combination locks that denote the high level of security; some doors have original numbers and acronyms which relate to their function.
The bottom level (Level 1) is divided into 23 rooms of varying sizes; most appear to have housed computer equipment. A number of rooms have halon gas fire suppressant systems.
The middle floor (Level 2) is divided into 14 rooms; a proportion of this floor is given over to air conditioning plant. Pursuant to s.1 (5A) of the 1990 Act it is declared that this air conditioning plant is not of special architectural or historic interest. In room 2/2 two of the 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 a nuclear explosion. The wartime map room and ‘tote’ board were housed on this floor; the steel plate may represent the infilling of the map well.
The top floor (Level 3) is divided into 8 large rooms of which the central room 3/1 was divided in 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 that notes: '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 is an emergency exit from the bunker 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 WWII fittings remain in place.
1980s DECONTAMINATION CELL
Steel blast doors at the outer entrance lead into a series of small interlocking rooms fitted with stainless steel fittings. Personnel passed from the entrance through compartments containing bins for the disposal of contaminated clothing and equipment before showering and changing into fresh clothes. The cell was controlled by a central console. Fittings appear to be intact with original signage in place. A further set of steel blast doors open into the bunker.
Listed building text is © Crown Copyright. Reproduced under licence.