He trained as an electrical engineer with Marconi's Wireless Telegraph Company, and was present at Dover in 1909 as Bleriot landed after completing the first air crossing of the English Channel.
Evans, with 11 of 12 pilots in his squadron becoming 'Hundred-Percenters' and receiving a letter of congratulations from Lord Trenchard, the Chief of the Air Staff.
Keith and his team presented their work showing that future aircraft should carry eight machine guns capable of firing at least 1,000 rounds per minute.
Having used slow motion film to record the penetration of bombs it was Keith who arranged the first such evaluation of machine guns.
Keith played a key role in the decision to introduce the French designed Hispano 20 mm cannon after a visit to France in 1936.
Early trials in Hurricanes and Spitfires found that the gun could jam during combat[20] but after modifications it became standard armament in later fighters.
The Hispano proved to be a good 'tank buster' and allowed Spitfires and Hurricanes to make effective attacks on ground targets and enemy shipping becoming one of the most used aircraft guns of the 20th Century.
[21] This invention was of immense value as the Second World War approached and fitted with up to four .303 Browning machine guns was standard equipment in British bombers.
Group Captain Keith was so moved by the letter that, with the mother's permission, it was anonymously published in The Times on 18 June 1940.
Keith served a short period as President of the Aircrew Selection Board before he was appointed the first Commanding Officers of Picton Gunnery School, Canada, in April 1941.
He managed to get six of the twenty points cleared up, but then he was recalled to England in April 1942 despite the Canadian Chief of Air Staff requesting that he be allowed to remain.
[30] "I Hold My Aim" is the motto of the Air Gunnery School and the title of Keith's book published in 1946, it gives a fascinating glimpse into the work of a man who, perhaps more than any other individual can be said to have 'put the fire in the Spitfire'.
[citation needed] He writes: Sidelined from the official history except for a footnote as the Commanding Officer of an anonymous young pilot Group Captain Keith died in 1946 in Surrey.