Vernon was commissioned into the Border Regiment and proceeded to France where he joined the Intelligence Corps and was attached to the Canadians. In October 1915 he was awarded the Military Cross after he managed to prevent a crashed German aircraft from being destroyed and retrieved a number of interesting documents from the crash site. The citation read as follows:
“For conspicuous gallantry in France on several occasions, notably on October 26th, 1915, when a German aeroplane had been brought down close behind our front line. The enemy commenced shelling the locality to destroy the machine, but Lieutenant Vernon at great personal risk, crept up to it, saved it from destruction, and brought in very valuable information”.

On 22 January 1916 Vernon was Mentioned in Dispatches and promoted to Lieutenant. Still with the Canadians, and promoted to Captain, Vernon was awarded the OBE, ‘in recognition of valuable services rendered in connection with Military Operations in France and Flanders to be dated 3rd June 1919’.