No 19 Squadron was first formed on the 1st of September 1915 and disbanded on the 31st of December 1919. It was reformed on the 1st of April 1923 at Duxford. On the 4th of August 1938 a Spitfire (K9789) arrived, the first of many. First blood with this new type aircraft was on the 11 of May 1940 a Junkers Ju 88 was shot down into the sea by a flight of  3 aircraft lead by a WF/Lt. W.Clouston. The Squadron fought well over the evacuation at Dunkirk where they lost 4 aircraft for the destruction of 13 E.A.'s. The Squadron destroyed 2 He 111's on the night of the 19th of June 1940. The first cannon armed Spitfire Ib's arrived at the end of June 1940 for field trials.
In July its task was convoy patrols at first but then joined in the Battle of Britain in earnest. On the 24th of July 1940 No 19 Squadron moved from Duxford to the Fowlmere Satellite Station. Hampered by the frequent stoppages they reverted back to Spitfire Ia's equipped with 8 browning machine guns in early September. During September 1940 No 19 Squadron flew with No 242 Squadron and No 310 Squadron as part of the Duxford Wing.