The Handley Page H.P.54 Harrow was a heavy bomber designed and produced by the British aircraft manufacturer Handley Page. It was operated by the Royal Air Force (RAF) and used during the Second World War, although not as a bomber. The Harrow was developed during the 1930s as a derivative of the Handley Page H.P.51, an unsuccessful monoplane bomber-transport hybrid. It was a twin-engine, high-wing monoplane with a fixed undercarriage. In 1935, the Air Ministry wrote Specification B.29/35 around the Harrow proposal, seeking a 'stop-gap' heavy bomber to facilitate the expansion of the RAF's bomber squadrons. Handley Page updated the design with new features and along with structural changes to enable more rapid construction. Despite incorporating several modern features, including hydraulically-powered turrets, steam-based cabin heating, and variable-pitch propellers, the performance of the Harrow did not match that of contemporary bombers such as the Armstrong Whitworth Whitley. On 14 August 1936, the Air Ministry ordered one hundred Harrows for the RAF. While the Fleet Air Arm also placed a separate order for one hundred Harrows, Handley Page did not have the capacity to produce these aircraft. On 13 January 1937, the first Harrow was delivered to No. 214 Squadron; by the end of that same year, all one hundred of the RAF-bound units had been delivered. By the end of 1939, the Harrow had been rapidly displaced as a frontline bomber, it was flown as a transport aircraft instead, which included its use as an air ambulance. It participated in several major actions, including an unorthodox defensive role for The Blitz in the winter of 1940–1941 and Operation Market Garden in September 1944. Limited numbers served through to the conclusion of the conflict, the RAF withdrew the Harrow in May 1945. As a transport, the Harrow was routinely used to convey equipment and personnel between domestic military bases across Britain, as well as to continental airfields prior to the Fall of France.It also occasionally undertook risky flights between England and Gibraltar; two aircraft were recorded as having been lost on this route. Harrows also operated in support of Allied forces in their advance into north-west Europe, evacuating wounded from the Arnhem operation during September 1944. Seven Harrows were destroyed by a low level attack by Luftwaffe fighters of JG 26 and JG 54 on Evere airfield as part of Unternehmen Bodenplatte, the German attack on Allied airfields in north-west Europe, on 1 January 1945, leaving only five Harrows intact. These were retired on 25 May 1945. The Harrow also served in a novel operational role at the height of The Blitz against Britain in the winter of 1940–1941. Six Harrows equipped 420 Flight (later 93 Squadron) which used lone Harrows to tow Long Aerial Mines (LAM) into the path of German bombers. The LAM had an explosive charge on the end of a long cable and the unorthodox tactic was credited with the destruction of between four and six German bombers. The experiment was judged of poor value and the planned deployment of Douglas Havocs in the LAM role was cancelled. Seven Harrows were also used by 782 Naval Air Squadron of the Fleet Air Arm as transports from June 1941 to July 1943, being used to carry engines and spare parts as well as passengers. For more details on development and operational experience, click here. 100 Harrows were built.