Mercedes' adventures with gull-wing doors span the epochal Fifties 300SL and last year's mighty SLS. But there was a third model, a car with a mystical resonance for Merc diehards, or fans of Seventies concept cars. The C111 sits alongside the likes of Pininfarina's Ferrari Modulo and Stratos Zero, and Bertone's Carabo as the king of car design at its most wildly expressionist. Every creative in the business will have pictures of these things on a mood-board somewhere.
But the Mercedes is different. The C111 first appeared at 1969's Frankfurt motor show, barely seven weeks after the first moon landing and looking like a vehicle that could repeat the feat. Far from being a piece of eye candy, it was a functioning experimental prototype powered by a radical rotary engine that posited a whole new approach to internal combustion.
In 1970, a further four were made, with various other iterations sprinkled throughout the next few years. In fact, a total of 14 would be made in all. Having abandoned the tricky rotary unit for a turbocharged diesel, Mercedes also installed its silky 3.5-litre V8 into a C111 at some point in the early Seventies, a car that recently starred in a film promoting Berlin fashion week and almost upstaged the stars of London Collections Men S/S 16. Not just with its orange-over-black retro-futuristic magnificence, but by being a proper runner.
We can verify this, because we've driven it, and not just round the block at walking pace. For a 45-year old concept car, the C111 is frankly astonishing, as thoroughly engineered as any other Mercedes of the period - and this at a time when its cars could rival Fort Knox for impregnability. Those wild doors and swooping body panels are the real knockout, and the interior has the hyperreal atmosphere Stanley Kubrick nailed so expertly in A Clockwork Orange.
But true to its experimental remit the C111's rear suspension featured a new set-up that would find its way into the next generation of Mercedes road cars. So it actually handles beautifully, riding and gliding over typically choppy British B-roads with unexpected aplomb.
It's also pretty fast, and its gearbox has a surprisingly treacly smooth action. In fact, the biggest threat to its wellbeing is likely to come from a Surrey pensioner in a Micra, so reluctantly we ease off. The C111 is insured for £5m, but its real value is incalculable. And deserved.
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