"Royal Air Force Bomber Command, 1941-1945" Avro Lancaster B Mark III, ED724 'PM-M', of No. 103 Squadron RAF pauses on the flarepath at Elsham Wolds, Lincolnshire, before taking off for a raid on Duisburg, Germany, during the Battle of the Ruhr. Three searchlights (called 'Sandra' lights), two of which are visible on the left, form a cone to indicate the height of the cloud base for the departing aircraft.