Absolutely correct. Derbyshire's Ladybower reservoir was completed in 1945, providing drinking water for the cities of the north and east Midlands. It is the largest of a chain of 3 massive reservoirs which are known collectively as the " Peakland Lake District".
Howden and Derwent Dams lie further up the valley. These two were used by the famous "Dambusters" in their experiments with Barnes Wallis' "bouncing bomb". Much of the film "The Dambusters" was filmed here.
Was going to ask the Dambuster question but thought it would then be too easy!! Z**