The single most distinctive feature of the Heyford is that its fuselage was attached to the upper wing rather than the lower one — the reverse of almost every other biplane. This gave the aircraft its unmistakable, top-heavy appearance, but it was a deliberate and clever piece of design.

Mounting the fuselage high left the lower wing free and close to the ground. That in turn allowed the bombs to be carried in cells in the thick lower-wing centre-section, where they could be loaded easily at low level, and gave the crew excellent fields of view and fire. What looked ungainly was, in engineering terms, a neat solution to the problems of a heavy night bomber.

Because the fuselage sat on the upper wing, the Heyford’s designers were able to build the bomb load into the thick centre-section of the lower wing, close to the ground. The bombs sat in cells within the wing rather than in a conventional fuselage bomb bay.

This had a real practical advantage: ground crews could load heavy bombs at roughly waist height instead of hoisting them up into a high fuselage, which made turning the aircraft around faster and safer. It is a good example of how the whole configuration of the Heyford flowed from the decision to hang the fuselage from the top wing.

The Heyford was powered by two Rolls-Royce Kestrel engines, elegant liquid-cooled V-12s mounted between the wings. The Kestrel was one of the outstanding British aero-engines of the interwar years and a direct design ancestor of the legendary Rolls-Royce Merlin that would power the Spitfire, Hurricane and Lancaster.

Giving the Heyford a top speed of around 140 mph, the Kestrels were reliable and well regarded. Their placement between the wings, close to the fuselage, made them relatively easy to service — another benefit of the aircraft’s unusual layout — and the type went through several marks as engine and equipment improvements were introduced.

The Heyford was defended by three Lewis machine guns: one in the nose, one in a dorsal position, and one in a retractable ventral turret. That ventral turret, which could be wound down beneath the fuselage to cover the aircraft’s belly and then retracted to reduce drag, was universally known as the “dustbin.”

Retractable ventral turrets of this kind were a feature of several British bombers of the period. By the standards of the coming war a handful of rifle-calibre Lewis guns was feeble defence, but for an early-1930s night bomber it was considered adequate, and the arrangement reflects the thinking of an age before the power-operated multi-gun turrets of the monoplane heavies.

The Heyford was designed and built by Handley Page, one of the great names of British aviation and a company with a long pedigree in heavy bombers stretching back to the Handley Page O/400 of the First World War. Its chief designer was George Volkert, a key figure in the firm’s work through the interwar years.

The Heyford was built to an Air Ministry specification of the late 1920s calling for a twin-engined heavy night bomber. It continued Handley Page’s tradition of large bombers and, in a sense, closed a chapter of it: the Heyford was the last biplane heavy the company — and the RAF — would field before the monoplane era.

The Heyford entered RAF service in 1933 and quickly became the standard heavy bomber of the mid-1930s force, equipping around eleven squadrons at its peak. For several years it was the aircraft on which Britain’s strategic bombing capability chiefly rested.

It was a familiar sight at the annual Hendon air displays and on exercises over eastern England, and it looked, at the time, thoroughly modern and formidable. That so front-line an aircraft could become obsolete so quickly is a measure of just how fast aircraft design was moving in the 1930s.

The Heyford’s greatest claim to fame has nothing to do with bombing. On 26 February 1935, near Daventry in the English Midlands, the physicist Robert Watson-Watt demonstrated that an aircraft could be detected by reflected radio waves — the founding principle of radar.

The aircraft used as the target, flown repeatedly through the beam of a BBC shortwave transmitter and successfully detected on a cathode-ray screen, was a Handley Page Heyford. This “Daventry Experiment” helped launch the crash programme that gave Britain its Chain Home radar network in time for the Battle of Britain. There is a fine irony in the fact that an obsolescent biplane played a part in the birth of one of the war-winning technologies.

For all its front-line importance in the mid-1930s, the Handley Page Heyford never saw combat. The pace of aircraft development in that decade was extraordinary, and by the late 1930s the fabric-covered biplane heavy was hopelessly outclassed by the new all-metal monoplanes.

The RAF withdrew the Heyford from front-line squadrons from around 1937 and had replaced it well before the outbreak of war in September 1939. It is one of those aircraft that was genuinely important in its day and yet, because its day fell in peacetime, is little remembered — a front-line bomber that never dropped a bomb in anger.

Once withdrawn from the front line, the Heyford was not immediately scrapped. Its size and docile handling made it useful for a range of second-line tasks, and it served on into the early war years as a crew trainer, a gunnery and bombing-practice aircraft, and a glider tug, among other support roles.

This was the common fate of the interwar biplanes: too obsolete to fight, but too numerous and too useful to throw away, they lived out their final years training the crews who would fly the aircraft that replaced them. The last Heyfords were retired during the early 1940s.

The Heyford’s career was marked by one particularly grim episode. In December 1936 a number of Heyfords returning to their bases in the north of England were caught by severe icing and fog, and several were lost in a single night in crashes and forced landings.

The episode was a stark reminder of the dangers of night flying in the era before reliable blind-flying instruments, radio navigation and de-icing equipment. For the interwar heavy-bomber crews, the weather and the limits of their own equipment were often a greater threat than any enemy, and accidents of this kind were the real hazard of the Heyford’s service.

The Heyford stands at the end of a long tradition of British biplane heavy bombers that reached back to the Handley Page O/400 of the First World War. For two decades the twin-engined biplane had been the standard shape of the RAF’s heavy-bomber force, and the Heyford was its final, most refined expression.

What replaced it was not another biplane but a wholly new kind of aircraft. The monoplane heavies that entered service in the late 1930s — the Whitley, Hampden and Wellington, and behind them the four-engined Stirling, Halifax and Lancaster — belonged to a different age. The Heyford was the last of the old line, flying front-line only a few years before the aircraft that would carry the war to Germany.

To understand the Heyford is to understand how fast aviation changed in the 1930s. When it entered service in 1933 it was a thoroughly credible heavy bomber; by the time it left the front line around 1937–38 it had been overtaken by a new generation that flew faster, higher and further and carried far more.

The Armstrong Whitworth Whitley, Handley Page Hampden and Vickers Wellington were all-metal, stressed-skin monoplanes with retractable undercarriages and power-operated turrets — a different world from the fabric-covered, fixed-undercarriage Heyford with its hand-held Lewis guns. The contrast between the Heyford and the aircraft that replaced it is one of the clearest illustrations anywhere of the monoplane revolution.

The Heyford was produced in several marks, distinguished mainly by their engines and equipment rather than by any change to the basic, unmistakable configuration. The principal versions were the Mk I, the Mk IA, the Mk II and the Mk III, which introduced uprated Kestrel engines and various equipment improvements over the production run.

These were evolutionary changes to a single design rather than distinct aircraft, and together they made up the roughly one hundred and twenty-four Heyfords built for the RAF. There were no export or civil versions: the Heyford was, from first to last, a Royal Air Force heavy bomber.

As with most RAF aircraft of the early 1930s, there is no reliable, transparent public figure for the Heyford’s unit cost, cost per flight hour or total programme cost. It was procured in modest numbers over a few years under the defence budgets of the period, and consistent lifetime cost data does not survive in a usable, comparable form.

Rather than repeat an invented number, we list the cost fields here as “not reliably recorded.” What can be said is that the Heyford was a relatively conventional, fabric-and-metal biplane built by an established manufacturer, and it would have been considerably cheaper than the complex all-metal monoplanes that soon replaced it — part of the reason the RAF was able to field it in useful numbers during the lean years of the early 1930s.

The Heyford’s importance is not that of a combat aircraft — it never fought — but that of a marker in the history of air power. It was the last biplane heavy bomber in RAF front-line service, the final expression of a tradition of British twin-engined biplane bombers reaching back to the First World War, and the aircraft on which Britain’s strategic bombing rested for a few crucial mid-1930s years.

It also has a genuine place in the story of radar through the Daventry Experiment of 1935. Taken together, its role as the RAF’s last biplane heavy, its walk-on part in the birth of radar, and its value as a perfect illustration of the biplane-to-monoplane transition make the Heyford far more interesting and important than its awkward looks might suggest.

No complete Handley Page Heyford survives. The biplanes were retired and scrapped in the late 1930s and early 1940s, and none was preserved intact — a common fate for interwar types that were obsolete before anyone thought to save them.

What does survive is a substantial fuselage section, preserved in the collection of the Royal Air Force Museum. Recovered and conserved as a rare relic of the RAF’s last biplane heavy bomber, it is, as far as genuine original Heyford structure goes, essentially all that remains — which makes it a precious link to an aircraft that was once the mainstay of Britain’s bomber force.