Presenter and engineer Rob Bell examines the defenses Britain put in place in 1940 to defend the country against the very real threat of a Nazi invasion.
Rob Bell explores the coastal defence network built to defend Britain's beaches, including a tower in Essex which controlled mines laid across the estuary.
With the blitz taking its toll, Britain had to keep it's manufacturing going. Shadow factories were born and were crucial in the production of ammunition.
Rob Bell looks at how the greatest invasion in human history was being prepared in Southern England and the buildings that helped with D-Day and Operation Overlord.
Britain needed to produce vast amounts of ammunition. Chatham Docks on the Medway saw 142 ships set sail, and bomber bases sprung up across the country.