No. 12 Squadron returned to England in June. It was stationed initially at RAF Finningley in South Yorkshire, before moving to RAF Binbrook in Lincolnshire during July 1940, when it was refurnished with Battles. Amongst other missions, the squadron carried out anti-invasion strikes against shipping in Boulogne Harbour in northern France, most notably on 17 and 19 August. The squadron was one of the last No.1 Group units to conduct operations with Fairey Battles. These took place on 15/16 October 1940, when No. 301 (Polish) Squadron bombed Boulogne and Nos. 12 and 142 Squadrons bombed Calais. By November 1940, the squadron had been re-equipped with the Vickers Wellington medium bomber, remaining for the time being at RAF Binbrook. The squadron moved again in 1942, to RAF Wickenby also in Lincolnshire, and soon after converted to operate the Avro Lancaster a heavy bomber.