His work concentrated on increasing the octane rating, which allowed the use of higher compression ratios, in particular the fuel additive tetraethyllead.
This work embraced the principal aero engine and automobile manufacturers in the U.K. and Europe, including the military air forces and commercial airlines.
At this time, he was also involved in developing the fuels used by Henry Segrave and John Cobb in their land and water speed record attempts.
With the coming of war, Banks entered the Royal Air Force Volunteer Reserve as a junior officer, being sent to work at the Aeroplane and Armament Experimental Establishment (A&AEE) at Boscombe Down.
His previous work having attracted the attention of Lord Beaverbrook, Banks was accredited as a "troubleshooter" and given special powers.