ROYAL AIR FORCE BOMBER COMMAND, 1939-1941. (C 1926) Vertical aerial photograph taken during a ‘Circus’ operation by No. 2 Group aircraft, showing smoke rising from direct hits on the generating plant of the power station at Pont-a-Vendin, France, during an attack by 18 Bristol Blenheim Mark IVs drawn from Nos. 18 and 139 Squadrons RAF. Copyright: © IWM. Original Source: http://www.iwm.org.uk/collections/item/object/205211305