Still based at RAF Northolt at the outbreak of war, No. 111 (Fighter) Squadron relocated to RAF Acklington, Northumberland, in October 1939. The squadron scored its first victory on 29 November, when Sqn. Ldr. Broadhurst shot down a Heinkel He 111. "Treble One" moved even further north to RAF Drem, East Lothian, in December 1939 in order to provide cover for the Royal Navy at Scapa Flow. By May 1940, No. 111 (F) Squadron had returned south to RAF Northolt due to the German invasion of France. On 16 May, a flight from No. 111 (F) Squadron joined a flight from No. 253 Squadron to form a joint unit, with one half deploying to France and the other remaining in Britain. "Treble One" flew defensive flights during the Dunkirk evacuation.