In April 1940, 22 Squadron moved to RAF North Coates in Lincolnshire and was involved in mine-laying operations, night bombing of enemy ports and, in May, daylight raids to try and stem the tide of the German "Blitzkreig". The squadron commander failed to return from a mission. Warburton did not fly operationally, and his few flying hours were mostly split between the Vildebeest and the Audax. He was then sent on a navigation and reconnaissance course at RAF Squire's Gate, Blackpool, which lasted until September 1940.