It was reformed on 20 July 1936 from 'C' Flight, No. 19 Squadron RAF at RAF Duxford, initially being equipped with Gloster Gauntlets, before a slow conversion to Supermarine Spitfires from August 1938. The squadron was part of No. 12 Group RAF in Fighter Command and was on readiness from the start of the war in September 1939. The first contact with the enemy was an attack on a Heinkel He 111 of the Norfolk coast near Cromer, the German aircraft subsequently crashed in Denmark. The squadron moved to RAF Horsham St. Faith after Germany's invasion of Belgium and the Netherlands, the squadron destroyed its first enemy aircraft on 12 May 1940 over the Hague. At the end of August the squadron moved to the south of England as part of the Battle of Britain, it operated from RAF Kenley, RAF Gravesend, RAF West Malling and by November to RAF Biggin Hill. By the time the Germans had stopped daylight bombing the squadron had destroyed 20 aircraft with another 17 probables and also damaged another fifteen.