This structure was completely below ground with raised entrances that would have been level with the surface at the time of construction. Subsequent development raised ground-level, totally obscuring any trace of the structure. As a result of this, shelter F7 was damaged by contractors during their sub-surface excavations and it was not possible to obtain complete measurements for the western entrance. Once shelter F7 was located and fully exposed, it was observed that the shelter was roughly aligned east to west. The eastern entrance was 55cm above the roof of the chamber and measured 6.45m long by 1m wide, descending eleven steps into a corridor. This was capped by concrete- covered corrugated iron that sat on a lip in the entrance walls that was 5cm deep on each side. It was not possible to ascertain the height of the western entrance above the roof of the chamber. Only one step survived descending into a corridor 1m wide, with a surviving length of 3.3m. Fragments of concrete with corrugated iron adhering to them would suggest that this entrance was also capped. Both corridors were 70cm wide and terminated in recesses that were 87cm deep and contained a centrally-located exhaust vent (10cm in diameter). The floors in both corridors were of poured concrete with five 60cm by 46cm slabs set into them. A white painted number (52) was on a facing panel of each entrance.
The central chamber was identical to shelters F1-F5 in terms of measurements and fittings. <1>