 In August 1939 , Johnson was accepted by the RAFVR and began training at weekends at the airfield Stapleford Tawney , a satellite airfield of RAF North Weald . There he received ground instruction on airmanship . Taught by retired service pilots of 21 Elementary & Reserve Flying Training School , Johnson trained on the de Havilland Tiger Moth biplane . Upon the outbreak of war in September 1939 , with the rank of sergeant , Johnson entrained for Cambridge . He arrived at the 2nd Initial Training Wing to begin flight instruction . He was interviewed by senior officers in which he said his profession and knowledge of topography , surveying and mapping would make him more useful in a reconnaissance role . The wing commander agreed , but nonetheless , Johnson was selected for fighter pilot training and given the service number <unk> with the rank of Sergeant . Johnson and several hundred others were entrained for Cambridge and the 2 initial Training Wing . While assigned here Johnson learned basic military drill , sometimes given the slang name " square bashing " . 
