It was designed by Miles Aircraft Limited and largely manufactured by Handley Page (Reading) Limited (who acquired Miles' assets) at Woodley Aerodrome, Reading, England. Originally submitted to the Air Ministry as a four-engined high-wing monoplane weighing roughly 16,500lb, the concept was well received by the Brabazon Committee, with Miles being issued with instructions to proceed. While development proceeded, various agencies argued over the aircraft's specification, leading to multiple attempts to change the design midway though, delaying progress and inflating costs. Delays over the placement of a firm order contributed to Miles' bankruptcy, after which its assets was acquired by Handley Page and formed into the subsidiary Handley Page (Reading) Limited to produce the Marathon. The Marathon represented several firsts, being Miles' first four engined aircraft as well as their first all-metal design; it was also recognised that the Marathon was the first British transport aircraft to comply with the stringent International Civil Aviation Organization (ICAO). However, the lack of commercial involvement in the specification to which the aircraft was built likely heavily contributed to the lukewarm response it received from such operators, with British European Airways (BEA) opting to not introduce the type despite buying seven of them with intentions of doing so. The largest operator of the Marathon was the Royal Air Force, where the type were primarily used as a navigation trainer. A total of 43 aircraft were built, 40 of the Marathon 1 production model built by Handley Page, of which 28 were later modified to T.11 military navigation trainer versions. Specifications below are for the Marathon 1 model. For details of the design and development, operational history and five variants, click here.