Commercial aviation got off to a slow start in the years immediately following World War I, and it was not until the mid-1920s that the pioneering civil airlines began to push out tentative long-range routes. In Britain the pace had been set by such companies as Aircraft Transport and Travel, British Marine Air Navigation Company, the Daimler Airways, Handley Page Transport and the Instone Air Line. Air Transport and Travel (Britain's first airline) ceased operations on 17 December 1920; the remaining four companies formed the building blocks from which Imperial Airways was created on 1 April 1924.

To Imperial Airways fell the task of establishing British commercial air transport on an economic basis, and with government backing it became possible - at least in a modest way - to begin the procurement of new aircraft and the survey and inauguration of air routes to link the British Empire. Needing more capacity than was provided by its 18-20-seat Armstrong Whitworth Argosy or 14-seat Handley Page W.10 aircraft, Imperial Airways acquired from the latter a total of eight aircraft designed specifically for use on the European and eastern sections of the Empire air routes.

Large biplanes, with a maximum wing loading of less than 48.2kg/m², they were of all-metal construction except for the aerofoil surfaces and aft fuselage, which were fabric-covered. The unequal-span biplane wings were devoid of flying and landing wires, braced instead by massive Warren girder struts, and having ailerons and Handley Page slots only on the upper wing. The tail unit was also of biplane configuration, with triple fins and rudders, and the heavy landing gear was of fixed-tailwheel type. Power plant comprised four supercharged Bristol Jupiter engines, two mounted on the upper wing and one on each side of the fuselage on the lower wing. All four engines were kept as near as possible to the aircraft's centreline, to minimise the problems of asymmetric flight in the event of an engine failure. For the first time in any British airliner the crew were accommodated inside the aircraft, in a compartment high in the fuselage nose which we would now call a flight deck. Within the main cabins - fore and aft of the wing area where the engine noise originated - passengers were provided with completely new standards of comfort and spaciousness. Those intended originally for eastern use (on the Indian and South African routes) carried six (later 12) passengers in the forward cabin and 12 in the rear, with space for 14.16m³ of baggage and mail amid-ships. The four equipped for the European routes (based at Croydon) carried 18 passengers forward, 20 aft and had 7.08m³ of baggage space.

The prototype flew first in November 1930. It was equipped subsequently for long-range service (H.P.42E, 'E' for Eastern) and named Hannibal. First of the H.P.42W ('W' for Western) for the European services was delivered in September 1931 and named Heracles. The remainder of this family of 1930s 'Jumbo' airliners had the names Hadrian, Hanno, Helena, Hengist, Horatius and Horsa. Remembered nostalgically in the early history of Imperial Airways, it was an unforgettable sight to see one climbing majestically away from Croydon or floating in on those enormous wings. Anthony Fokker once commented that H.P.42s had built-in headwinds, but their cruising speed of around 161km/h, excellent handling at low speeds and robust structure ensured that they were able to boast a decade of fatal-accident-free flight before being withdrawn from civil airline service on 1 September 1939.