The aircraft that is probably the quintessential 1930's imperial airliner.
In 1928 Imperial Airways tendered for 3 and 4 engine for European and Eastern routes. One of the requirements was for a very low stall speed, which meant a slow landing speed, but also to a slow cruise speed.
For the 4-engined design, HP went back to their V/1500 design. with a Bleriot-style engine grouping. Wing bracing wires were replaced by an external bracing truss, and the whole cabin and very tail were duralumin moncocque structure. The H.P.42 was to be the Eastern model, and the almost identical H.P.45 the Western. Externally the only significant differences were the use of 2x 2 bladed propellers in the Eastern aircraft, and 4 bladed propellers in the Western - as a 2 blade would be easier to transport to the Middle East for repair and replacement in future. In service Imperial Airways service all aircraft would simply be referred to as H.P.42's.
Initial testing showed the purely trussed wing did not pass stresses correctly leading to the outer truss collapsing, so outer bracing wires were added to the design.
Although travelling at the same speeds as airliners of 10 years previous, the H.P.42's carried 3 times the payload. Up until WW2 they flew 2.3 million miles without a single fatality, all while serving 7-course dinners on longer routes (4-course meals were the standard) with 2 stewards in absolute luxury. 1937 an H.P.42 became the first commercial aircraft in the world to have flown 1 million miles in passenger service.
With only 1 crash, the remaining 7 H.P.42's were still in service with Imperial Airways at the outbreak of WW2. All aircraft were impressed into the RAF and the European aircraft provided support for the British Expeditionary Force in France. Service in the RAF was not as successful as civilian service. The original "Hannibal" was lost without trace from Oman, and the remaining 3 Eastern aircraft returned to Britain. One crashed in a forced landing, and two were destroyed on the ground in a storm. Another forced landing and another storm left only the "Helena" who was damaged beyond repair in a forced landing. So by 6 December 1939 the H.P.42 fleet was no more. An attempt to repair "Helena" was made in 1941, but the airframe was so corroded the aircraft was dismantled and used as an office.