Blackout

The blackout was the darkening of London's streets to deny enemy aircraft clear targets, which was implemented early into World War II by the government of Britain, fearing attacks from German bombers. (AUDIO: The Oncoming Storm)

Blackout rules stated that all windows were to be covered, rooms were to be left in darkness, and no headlights were to be used, or torches or cigarettes lit in the open air. The illumination of the Big Ben was also switched off. (PROSE: The Time Traveller's Almanac)

Ultimately, the restrictions on car headlamps and street lights at night resulted in more deaths from traffic-related accidents than from air raids. Blackout regulations were relaxed thereafter. (PROSE: Just War)

People were very worried about light being turned on as shown when it was instantly told to people to turn them off. (TV: The Empty Child/The Doctor Dances) Even the Ironsides that Edwin Bracewell "invented" had their luminosity dischargers were covered up. (TV: Victory of the Daleks)