Air officers discuss plans to bomb England . Air defence week opens . Nearly 400 machines are engaged in mimic air battles in which London is the central objective in the Air Defence Exercises week which has just commenced . Fighter aircraft representing Northland ' s forces are attempting to defend London and the South East of England against attacks by bombing machines of Southland . The purpose of the manoeuvres is to give combined exercises to all branches of the Royal Air Force . Photo shows , Squadron leader C M Cahill ( right ) of No 15 Bomber squadron in front of the squadrons Hawker Harts discussing with his pilots plans for the night raid over England before taking off from RAF Horsham St Faith . 22 July 1935