At the outbreak of World War II Flight Refuelling had two civil registered Harrows in Canada for trials. The RCAF bought them, serial 795 as spares for 794. 794 was withdrawn in November 1941. Photo from: Library and Archives Canada

In-flight refuelling trials over Calshot with Short S.30 Empire G-AFCU Cabot. The receiver and the tanker each deployed a cable with a grapnel to establish a line between the two and then the hose could be reeled in by the receiver. 16 transatlantic airmail flights were made by Cabot and G-AFCV Caribou using this method just before the outbreak of the war. Just like the catapult ships used by the Germans, the Harrow tankers did not travel far, but allowed the mailplanes to fly with a heavier fuel load. Photo from: Nationaal Archief (Netherlands)

The prototype of the Harrow, an interim heavy bomber, at the HP factory airfield. 100 Harrows equipped five RAF bomber squadrons in the course of 1937, but were replaced by 1940 and subsequently used mostly as transport aircraft. K6933 to G-AFRG in 1939, one of three used in in-flight refuelling trials.