The Battle of Britain Bunker is a Grade I Listed building. Construction of the building began in late 1938 and was completed in August 1939. The bunker is built into a hill sloping down to the river Pimm and is subterranean. It is accessed by a flight of steps from the adjacent road and has an emergency exit is located lower down the site near to the public path alongside the river.

The bunker is constructed from reinforced concrete, the entrances to the two flights of stairs are clad with asphalt and are visible above ground level. The building was constructed to be resistant to aerial attack and comprises of two independent plant rooms with their own power supplies, which provide air filtration and ventilation, toilets operated by compressed air, and telecommunication cables. The plant rooms serve the central two storey command centre which contains the plotting room which displays aircraft positions.

The building played a key role in the Battle of Britain in coordinating the deployment of aircraft against the German air offensive. Information from observation points over the south of England was received and displayed in the plotting room where a response then issued.

The building has suffered incidents of flooding extending back many decades. Hydrostatic pressure and ground level storm water surcharging the entrance area have resulted in water descending the entrance and exit stairs. There are also recurrent damp problems, where water has also entered the plant rooms through the ventilation shafts.

MAA’s proposals include drainage improvements by redesigning the surface water drainage and discharge system and the installation of new buried land drains. Lowering curbs and grassed areas will allow flood water to drain away before reaching the entrance steps. The existing drain south of the bunker will also be extended to discharge further away from the building.