Imperial Airways approved Handley Page's proposals and ordered four aircraft of the two variants to serve as the new land-based long-distance flagships of its fleet.

Following their introduction into Imperial Airways service, they formed the backbone of the airliner's land-based fleet through most of the 1930s and, along with the company's numerous flying boats.

In 1928, Imperial Airways invited submissions from the British aviation industry for a replacement of its de Havilland Hercules and Armstrong Whitworth Argosy landplane airliners for use on its major long distance routes across the Empire.

[3] Imperial specified that the aircraft's stall speed would not exceed 52 mph (84 km/h), and it was to be able to fly hands-off and be able to maintain altitude with one engine out, for a given range.

British aircraft manufacturer Handley Page, who had already established a reputation for large airliners, began work on designs to fulfil it.

Automatic slots were fitted to the top wing, which benefited from a new construction approach involving single z-section spars and planking, of duralumin.

[10] Slot-type ailerons are also used, each with four hinges and supported by four box-section brackets and both statically and aerodynamically balanced, making for relatively light control forces.

[13] The upper engines were placed as close together as permissible by the diameter of their propellers and were mounted on rigid duralumin plates attached to the rear wing spar with welded steel tubing.

Other features aimed at improving passenger comfort including spacious cabins, wide windows, and full onboard services.

[19] On 14 November 1930, the prototype, now named Hannibal and registered as G-AAGX, was flown by Squadron Leader Thomas Harold England for the types first flight.

The extremely high cost of air travel at this time usually limited flights to members of high society, such as royalty, celebrities, and senior business figures and the H.P.42/45 fleet were viewed as Imperial Airways' flagships and were accordingly provided with a luxurious onboard service and an elaborately decorated interior.

[1] A key requirement of Imperial Airways was for its airliners to land safely at low speed, on the grass or unpaved airfields common at the time.

During 1951, Peter Masefield wrote, "The trouble about a slow aeroplane with a really low wing loading is the way it insists on wallowing about in turbulent air ... One of the reasons why seven times as many people fly to Paris to-day, compared with 1931, is that the incidence of airsickness in modern aircraft is only one-hundredth of that in the pre-War types.

"[22] Another writer remembered "I had quite often been landed in a '42' at Lympne to take on sufficient fuel to complete the flight (from Paris) to London against a headwind – 90 mph (140 km/h) was its normal cruising speed.

[24][1] In 1933, after several had been lost or damaged in accidents, Imperial attempted to purchase two more H.P.42s, to be powered by Armstrong Siddeley Tiger engines, but would not accept Handley Page's quoted price of £42,000 each, which was much higher than the original price of £21,000 in 1931, so, instead, they ordered two Short Scyllas, a landplane version of the Short Kent flying boat.

A forced landing was made at Five Oak Green, Kent where the aircraft suffered further damage to a wing and another propeller, and the tail was ripped off by a tree stump.

[27] Hannibal was again damaged at the RAF temporary landing ground at Semakh on the Sea of Galilee on 17 November 1932, by strong winds.

[28] It disappeared over the Gulf of Oman on 1 March 1940, with eight aboard, including the First World War ace Group Captain Harold Whistler and the Indian politician Sir A. T.

[33][28] G-AAUC was originally named for Hecate, the Greek goddess but was soon renamed for Horsa, conqueror of Britain and brother of Hengist.

G-AAUD, production number 42/3, was named for the Carthaginian, Hanno the Navigator, who explored the Atlantic coast of Africa around 570 BC.

It appeared in the fifteen-minute 1937 Strand Film Company documentary Air Outpost, landing at Al Mahatta in Sharjah, now in the United Arab Emirates.

Returning from France on 7 November 1939, the aircraft was unable to find its destination at Exeter due to bad weather and was forced to make an emergency landing at Tiverton Golf Course during which, it hit two trees and was destroyed.

[citation needed] G-AAXE was originally named for the Hesperides, but was soon renamed after Hengist, brother of Horsa and legendary conqueror of Britain.

Hengist was caught in an airship hangar fire and burned at Karachi, India on 31 May 1937, making it the only H.P.42/45 not to survive until the Second World War.

[16][19] Original blueprints and other source material from the era are available and while a replica can be built to be airworthy, modern safety regulations prevent carrying paying passengers.