The ‘Shadow Factory Tunnels’ are the remnants of Lord Austin’s secret plans that were hatched to bolster British military might in the face of German military aggression in the arms race that led up to the start of the Second World War.
This was where munitions workers produced the Merlin engines that powered the Spitfires and Hawker Hurricanes used to regain control of the British skies during the Battle of Britain in 1940.