Another visible remainder of the wartime activities is a large mound on the south-western edge of the range. This seemingly unimportant hillock was a replica German submarine bunker, built by the British Army here to try and develop a bomb capable of penetrating the thick concrete walls of the sub bunkers. By all accounts, they were never successful!

A few metres beyond (on the western side) of the bunker mound is a large crater, now a pond, which was made by the biggest bomb ever dropped on UK soil – Ten Ton Tess, also called a Grand Slam bomb.
This gigantic 10,000kg bomb was tested here on Ashley Range, and the next day was used during a raid on Germany, dropped from a Lancaster bomber. The idea of the bomb was to cause an explosion large enough that the shockwaves emulated an underground earthquake, and by all accounts it worked!