The initial impression was of a long, low earthen mound (approx 7m by 11m) with concrete walls and entrances visible at either end, aligned NE to SW. The south-west entrance was made inaccessible by a concrete cover, but access was possible through the north-east entrance down a flight of six
concrete steps. Extensive photography of the exterior and interior was undertaken, and hand-drawn plans were made. A Total Station survey was undertaken which produced a plan showing:
• The extent of the grass-covered mound
• The top of the grass-covered mound
• The two entrances
• A contemporary slab pathway leading to the north-east entrance
• The only surviving sub-surface exhaust vent
The earth mound stood approximately 1.2m above modern ground-level at its highest point and was partially obscured on the western side by a mature tree. The top of the south-west entrance was 20cm above the roof of the chamber – it was not possible to observe this calculation at the north-east entrance. A slab pathway made of 60cm by 60cm slabs was laid at an angle to the north-east entrance. No concrete cover was present at the north-east entrance and a thick layer of moss indicated that there had not been one for some time. There was, however, a 5cm deep lip around three sides of the entrance walls. Access to the shelter was down the flight of six steps on the north-eastern side, into a short corridor. The dimensions of this entrance were 5.4m long by 1m wide in plan. The internal width of the corridor was 70cm, indicating that the entrance walls were each 15cm thick. Directly ahead was a recess (approx 87cm deep by 70cm wide) with a centrally-positioned circular hole (10cm in diameter) in the roof. This is interpreted as either an air vent or an exhaust vent for waste gases.
To the left of the corridor was a wooden door (72cm by 1.97m) set into a dividing wall and opening in towards the corridor. Eighty per cent of the external face of thedoor was covered by a metal plate, which was attached to the door with screws, and painted white. A simple curved iron latch was affixed to the left-hand side of the door approximately one-quarter of the way down. The door was supported on two hinges, each 30cm from top and bottom, screwed directly into the concrete wall. A painted square divided into two red and one blue upright bars with the letters ‘S3 COY (U)’ above it was positioned in the centre of the door at the same height as the handle.
Upon opening, it was clear that the door was set into a recess so that it could not be opened or blown into the chamber by an explosion. The internal face of the door was painted off-white and had a replacement panel covering the lower left-hand quarter. An A2 poster held in place by masking tape covered the upper part of the door. On this was printed, in upper case:
MILITARY NOTICE
NO SMOKING
NO FIRES
While the typeface suggested that this was contemporary with the shelter, there is a strong possibility that the door is a later addition to seal the shelter and that originally the internal entrance was either open or sealed by another type of door. There was no in situ door in the southern corridor, but iron hinges were present.
The central chamber externally measured 7.38m long by 2.45m wide by 2.45m high with an internal measurement of 2.24m at the widest point and 1.68m at its base. The sub-circular chamber was painted white and was constructed of reinforced concrete, with evidence of shuttering being clearly visible. It would appear that an internal frame of angled planks was constructed within a larger box and the void filled with steel andconcrete. This produced distinct panels of concrete – 15 facets, plus the floor – around the circumference of the chamber. Twelve 60cm by 60cm concrete slabs extended down the centre of the chamber beneath which was a channel, 18cm deep by 46cm wide, and lined with wood, which was divided into five sections.
A light switch was located at the western end of the chamber with a metal-cased wire leading up the wall and along the chamber roof to a centrally mounted bayonet light fitting. It was uncertain if this was contemporary with the shelter’s construction. Four more of the exhaust vents were evenly located in the roof. The whole structure, with the central chamber and two sets of stairs at either end, displayed an inverse symmetry in construction, as shown by the plan. <1>