This is a fasinating article about the lengths needed to compensate for turning the lights off in London during the war
One of the more interesting aspects of urban life during the bombing raids of World War II was the clever and strategic re-designing of the London street-scape so that residents could live in a state of blackout.
By turning off the lights at night, residents could hide the city from aerial view and thus leave Nazi bombers flying around in the darkness, unsure of where to drop their bombs. It was a different form of camouflage, one that hid the city against the surrounding landscape by plunging its streets and buildings into darkness.
You can read all about it here : http://gizmodo.com/how-london-was-redesigned-to-survive-wartime-blackouts-1494077058