Parts of the Coleshill site was excavated by The Ridgeway Military and Aviation Research Group.
These images were taken when the "observation post" in Cuckoo Pen Wood was being excavated.
It was the normal double-skinned chamber, except that the inner walls were not corrugated iron, but asbestos.
We eventually found that the chamber had an access from the top of a shaft leading to one of the old water tunnels. A pot-holer friend surveyed the tunnel and found that it led to a point below the site of the former kitchens. Following a fire in the original ammo store during the war, we think this was the replacement, carefully sited some distance from the house and accessible only by discrete means.