A sole prototype, designated Handley Page HP.38, was produced, performing its maiden flight on 12 June 1930 and commencing service trials shortly thereafter.

The replacement of the type had commenced during 1937 as more capable bombers were introduced during a major rearmament push for the RAF; the Heyford was formally declared obsolete in July 1939, barely two months prior to the outbreak of the Second World War.

By 1928, the Air Staff had concluded that, while one single airframe could be suitable versatile to meet the majority of its needs, a dedicated nighttime bomber was required.

[2] In response, the Air Ministry issued Specification B.19/27[clarification needed], which sought a heavy bomber for nighttime operations to replace the Vickers Virginia.

The requirements listed included the use of a twin-engine arrangement, positive stability, ease of maintenance, good manoeuvrability, avoidance of excessive pilot fatigue, an adequate self-defense capability, sufficient carrying capacity for up to 1,546 lb (700 kg) of bombs, and to traverse a distance of 920 miles at a speed of at least 115 mph (185 km/h).

[2] A new recruit to the company, Raymond Sandifer, played a crucial role in this substitution process, which included steel tubing and aluminium fuel tanks.

Other changes included an alternative undercarriage configuration that produced less drag, adjusted wing stagger, and revisions to the positioning of the fuselage.

[6] The prototype was completed during May 1930; it was powered by a pair of Rolls-Royce Kestrel II engines, each capable of producing up to 525 hp (390 kW), that drove a set of two-bladed propellers.

Numerous improvements and changes were suggested by test pilots and reviewing officials alike, including enlarged radiators, thicker skin, and a revised cockpit design.

[8] Handley Page were under pressure to proceed rapidly, partially due to competition from the Vickers Type 150 and the Fairey Long-range Monoplane; the prototypes of both these rivals suffered separate accidents, which gave extra time to refine the HP.38.

[10] As a consequence of the talk at the League of Nations of abolishing bombing, military planners opted to delay the awarding of a production contract; at one point, Handley Page was considering laying off numerous staff involved with the HP.38 over this uncertainty.

However, the Japanese invasion of Manchuria and a lack of consensus among the Geneva Disarmament Committee led to the Air Ministry issuing instructions to proceed with an initial batch of five aircraft, designated "HP.50 Heyford".

This arrangement provided a favourable field of fire for its defensive weapons, which were positioned on the nose and dorsal sections, along with the ventral retractable "dustbin" turret,[14] each of which were armed with a single .303 in (7.7 mm) Lewis light machine gun.

[18] As part of the RAF's expansion plan, follow-on orders were placed for 70 Heyford IIIs during 1936, which were equipped with steam condenser-cooled Rolls-Royce Kestrel VI engines.

102 Squadron, returning for Northern Ireland encountered fog and icy weather conditions on their approach to RAF Finningley, Yorkshire.