Aged 30 at the height of Word War 1, WO Bentley was supervising production of his 24.9 litre BR2 rotary aero engine. Already a Lieutenant in the Royal Naval Volunteer Reserve (RNVR), a cadre of civilian volunteers, which had quick means of promoting wartime officers in the Royal Naval Air Service (RNAS) he had been sent to Derby, where Rolls-Royce made air-cooled Renault aero engines, to meet Ernest W Hives (later Lord Hives) with whom he formed a bond lasting twenty years.