As stated before, when the RAF rejected the Pterodactyl as too heavy & slow for a fighter, Westland built a twin version (known to the test-pilots as the "Twinner-Dactyl") as a Bomber-escort for the RAF's Heavy Bomber squadrons (currently flying the Handley-Page Heyford) -- it was accepted & went into service as the WHF-1 "Twin-Dactyl". The RAF squadrons practised their mission profiles often with the opposing light-fighters coming from other squadrons - it was on one such mission that a Twin-Dactyl collided with a Heyford, bending the Dactyl's starboard wing forward to an alarming degree. The Heyford spiralled down crashing in a field - the crew escaping with moderate injuries. The twin-Dactyl however performed a sight never seen before .... initially entering a flat spin ... normally impossible for that design ... & that no-one thought would end. The pilot fought valiantly then gave up and the three crew prepared to bail-out .... if they could against the centrifugal forces. On letting go of the control-column, the aircraft suddenly straightened out for a second, then performed what can only be described as a one-turn, nose-up 360deg spin & vertical "jump" before starting to fall again. The crew didn't care for these antics & with a seriously damaged aircraft they wisely opted to complete their exit.
Examination of the wreckage brought nothing to light - all damage was consistent with a mid-air collision & subsequent crash. However the reports on the bent aircraft's behaviour seemed to match the thoughts of Westland's wing-design theoretician - ie:- that a wing of certain orientation could behave in some amazing ways .... the wing & attachments would have to be strengthened considerably but it was quite possible that a revolution in fighter tactics was on the cusp of attainment. A prototype was modified from a standard Twin-Dactyl & tested in every possible way -- it was found that by advancing the starboard-side main-plane, the observed gyrations were possible. The asymmetric power application (both engines being on one side of the aircraft) made the turn much better to the left than to the right and this suited pilots. ((it was a long-standing physicological rule, known to many Aces, that is more "natural" for people to bank left, than right, giving those who knew about it an advantage)).
The Westland "Zag-a-Zig", named after the wing plan-form, was a radical departure from normal aircraft design & was the first ever "swing-wing" aircraft to fly. Due to its deliberately stable / unstable flight-characteristics (depending on the pilot's selection in flight), it could evade even the most nimble light-fighter sent to destroy it. It was immediately seen that a normal RAF pilot wouldn't have the required training to fly this aircraft -- it was thought that at least 3yrs of aerobatic training was necessary for full proficiency -- a standard that very few pilots had. An ideal opportunity to test the aircraft in a real arena came with the Spanish Civil War and as war with Germany was already seen as inevitable, the RAF started offering pilot's commissions to all who qualified as advanced aerobats. Many barn-stormers saw that their world was coming to an end -- stunts were becoming "old hat" & "routine", crowds, & income from them, were getting smaller and many of their sort, ex-WW1 pilots, were getting too old for this type of activity. Most accepted the RAF's offer of a regular pay-cheque -- those still young enough to have fast reactions were offered Active pilot's commissions in a special squadron - the others were offered commissions to train the increasing number of fighter-pilots now being sort for the war ahead.
A small batch of twenty Zag-a-Zigs were built &, after a year of secret training, five were sent to Spain to observe developments there as part of a League of Nations observer team -- it was rightly seen as a testing-ground of the future war. Being prohibited in joining in any fighting apart from the most dire self-defence, these Zag-a-Zigs of 000 (Triple-Zero) Sqdn -- whose pilots were all ex barn-stormers -- had the turrets removed & faired over - only twin, fixed 303's being mounted in the nose of the right-hand fuselage. 000 Squadron went as ordered, hoping to be challenged by all sides in the air as interlopers. Being prohibited from firing their guns didn't faze them - they were confident in their mounts to evade anyone that got on their tails & had their secret banks of ten Delco-Remy "air-guns" either side of the right fuselage & two bottles of compressed-air mounted inside to "fire" them.
They soon made a nuisance of themselves -- flying above the general area, they waited for the protagonists to clash. Then they would dive and fly in & out of the ensuing melee, causing much annoyance to those who had just lined-up on an enemy machine. The Polikarpovs welcomed this interruption to their deaths, but the pilots of the Me-109a's of the Kondor Legion's Herman Goring Squadron saw it as un-Knightly behaviour & unforgivable poaching on their ground. The Me-109's thought they'd teach these arrogant Englishmen a lesson - they knew that their aircraft were faster & they could catch them in a run any time. But the Englishmen didn't run .... in fact they slowed down a bit & tempted the Messerschmits to shoot at them by lazily waggling their wings & waving to them. This was too much !! One pilot, a holder of the Knight Cross with 35 kills to his credit in the Great War, decided to shoot the offender down. He positioned himself behind the Zag-a-Zig & closed in .... the British pilot held his position, continuing to wave at him !! Just as he was about to fire his guns, the Zag-a-Zig disappeared !! His wing-man warned him -- "Ze Englander hast spun below you !"
The pilot had moved the lever of the wing-actuation mechanism to "U" for unstable & the right wing swung forward, the spoiler popping out as it did so. The Zag-a-Zig dropped the wing-tip & the aircraft performed it's special turn - a fast 360deg spin & extremely rapid climb, temporarily blacking out the pilot, it put him right behind his enemy in just a fraction of a second.
"Aaaargh-oooooh-Gaahh !!!", "Aaaargh-oooooh-Gaahh !!!" went the Englander's "air-guns" -- the extremely loud, old-fashioned, car horns blasting the Messerschmitt pilot with sound, urging him to get out of the way of the Zag-a-Zig, now quite unexpectedly, immediately behind, causing the German pilot to soil his clothes ...
The lessons of the Spanish Civil War had indeed been learned ... by the German Pilots. Triple-Zero Squadron had the desired effect -- zero "kills" & zero losses in Spain resulted in zero aggression towards the RAF bombers on their way to Keil when-ever they were in the air.
An asymmetric swing-wing ....