The Mercedes supercar blank cheques couldn't buy

Blank cheques: that's what Mercedes-Benz was presented with when it unveiled the C111 at the 1969 Frankfurt motor show.

It's an understatement to say the prototype caused a sensation at the time, eager customers thrusting cheques at the staff on stand in Germany in a bid to be the first to buy one.

Nobody ever would. That's probably why the gullwing wedge is a supercar enigma, destined to appear prominently in Mercedes-Benz’s own literature, Top Trumps cards and coffee table exotic car books ad infinitum, but never, ever, to be parked in a customer’s garage.

Mercedes-Benz certainly wasn't short of the resources to build it, nor, as all those cheques demonstrated, was there any question of demand. Why it was never sold remains something of a mystery; it's said that the board got cold feet as the company was, at the time, very heavily focused on safety.

Hence a mid-engined, fibreglass-bodied supercar didn’t quite fit with the firm’s image. It is also said that the C111’s unusual engine specification was a problem for production: the Frankfurt show car was powered by a triple-rotor Wankel engine over which engineers expressed concerns about maintenance and heavy fuel consumption.

Time would, perhaps, vindicate the company’s decision not to sell the C111, as its unveiling wasn't long before a global fuel crisis that would have inevitably punished sales, even if rival supercars from niche firms would weather that particular storm.

The C111 might not have ever reached the showroom, but Mercedes-Benz did build it. A total of 14 examples were constructed, of which around 11 are said to remain.

The cars were used internally as experimental vehicles and some of the technologies tested are still apparent on Mercedes-Benz vehicles today. The firm followed that original C111 Frankfurt car with the C111 II, unveiled at the 1970 Geneva show.

Changes to the styling brought a new bonnet with scalloped vents in its centre for improved cooling, while the engine gained an additional rotor, increasing output to 265kW. That would allow the C111 to reach 100km/h in 4.8 seconds, while its top speed was claimed to be 300km/h.

They were sensational numbers in the 1970s, bettering its most obvious mid-engined contemporary, Lamborghini’s Miura P400S, by nearly 20km/h at the top end and nearly a second in the benchmark sprint.

Later C111s would make even those figures look pedestrian, as Mercedes-Benz pushed its wind-cheating wedge faster and further still, breaking records at the Nardo test track in Italy as part of its experimental remit.

Those petrol-fuelled Wankel engines were replaced with turbocharged, intercooled five-cylinder versions of the company's OM617 60kW diesel engine, its power swelling to 140kW, then latterly 170kW.

The bodywork was revised too, with a longer nose and tail for improved stability. The combination of those changes allowed the C111 to claim nine diesel and petrol speed records. Seduced by the idea of yet more records, the engineers gave the C111, in its fifth and final incarnation, even more radical streamliner-styled bodywork and a turbocharged 4.8-litre petrol V8 engine with 368kW.

These changes allowed the C111 to achieve an average lap speed around Nardo’s 12.5km circular track in a scarcely believable 403.7km/h with Dr Hans Leibold driving. That was in 1979; if the C111’s status was already the stuff of legend, then that day around Nardo absolutely cemented it.

There will be no speed records today, not least because the C111 parked outside has a sticker on the dashboard asking that it not be taken above 130km/h.

It's one of the C111 IIs from 1970 and it’s the first time I’ve ever seen one away from a museum or static display, but it’s parked outside Mercedes-Benz World in Brooklands, England, and I’ve just been handed the keys.

The phone call a few weeks earlier was brief: a C111 would be over in the UK for a few days to visit the Goodwood Festival of Speed and London Fashion Week, and would I like to drive it? The answer was obvious, though seeing it under the summer sun at Brooklands it’s difficult to get over the enormity of what I’m just about to do.

Matthias Chwal from Mercedes-Benz’s Classic Centre is its custodian for a rare trip out of the museum, walking me around it, discussing the various technical highlights of the dramatically-styled machine and casually dropping into the conversation the fact it’s insured for about €6m (about $9 million). No pressure, then.

This particular car wasn’t used for record breaking, but testing brakes; it was instrumental in Mercedes-Benz’s development of anti-lock braking for its road cars. Imagine being the test engineer in the early '70s being handed the keys to this as your company car.

It was also used for testing windscreen-mounted aerials for radio reception, the thin orange line around the windscreen betraying the existence of the once cutting-edge technology.

Chwal opens the back to point out the independent, multi-link rear suspension and the fitment of a period accurate 3.5-litre M116 V8 petrol engine. It would have powered the R107 350 SL back in the '70s; Mercedes-Benz fitted it to the C111 here in place of the Wankel rotary units for reliability.

With just 147kW it’s not got the prodigious pace those show cars promised, but with a lightweight fibreglass body it’s still able to offer respectable, if not shocking, performance.

Lifting the gullwing door reveals a cabin that, given its experimental, tiny production-run status, looks remarkably complete. The chequer-plaid seats are so evocative of the period, complemented by the lattice-rimmed steering wheel, clear, simple instruments and upright Becker radio to which that windscreen-mounted aerial was fitted.

No radio is needed today, as turning the key rouses that lazy V8 into life, the thin fibreglass firewall meaning the cabin is filled with the evocative throb of a basic, naturally-aspirated engine. The rev counter has a redline of 6000rpm -- some way short of the 10,000rpm the needle could sweep around to with the Wankel fitted in the back.

The clutch is light, the long gearstick topped with a delicately proportioned knob displaying the dogleg pattern. Selecting first requires a push of the button on top of the stick before the bespoke ZF five-speeder allows it to be selected. The shift is light, if long, it needing practice to be hurried, though the pedal positioning does allow for heel-and-toe blips to ease in the gear when downshifting.

It might be a low, dramatically shaped supercar, but visibility out of it is surprisingly clear, which, given the busy traffic around Mercedes-Benz World, is appreciated. Our destination is Brooklands, and an area of banking that formed part of the world’s first dedicated motorsport track is a fitting location for Richard Pardon to point his camera at Mercedes-Benz’s unsold icon.

radio aerial
The C111 looks great on the steep concrete that made up the Brooklands circuit. It’s a delicately styled car that, small wheels and pop-up headlights aside, still looks contemporary. The proportions are neat if not pretty or with the flair you might find in one of its Italian rivals. The C111 Germanic in its precision, though no less beautiful for it.

The front might be its most recognisable angle, but it’s the rear that is most beguiling. The slim buttresses, the beautifully simple scalloping fore of the rear wheel and the concave engine cover painted in black look particularly smart. The rear, with its upright, near Kamm tail is slatted between simple round lights, while the exhaust outlet is integrated into the rear bumper.

The metallic orange hue (which was originally described as ‘rosé wine’) contrasts with the black perfectly, helping define the C111’s shape, lengthening and lightening it. Given it was built to hack around test tracks trying out new technology, it’s needlessly beautiful, though what an incredible time the engineers must have had with it.

Our time on the road with the C111 is short, limited to a brief run around busy Surrey roads before an hour on Mercedes-Benz World’s test track. Chwal looks nervous, but to push such a valuable, important car hard would be needlessly selfish, though even so-restrained the C111 reveals a lot of detail about how balanced and enjoyable it is to drive.

The steering is light and accurate and it's possible to feel everything running under those Michelin XWX tyres. The ride is impressively smooth, too, not least because of those tyres' sizeable profile.

The C111 featured developmental anti-dive suspension, which is obvious when approaching corners on the brakes, though once off the brakes and turning in, the lean is demonstrative of an era when suspension technology was otherwise fairly crude.

It rolls into the bend in what initially feels like an alarming fashion, but it’s resolute once there, grip good, feedback high and there's even a touch of throttle adjustability if you back off. The brakes are strong and full of feel, though the gearshift remains tricky.

This C111 is not hugely quick, but there’s so much fun to be had driving it. I can't help but wonder if another 120kW might corrupt it, but it sure would be very interesting to discover. I’ll never know, though the thought of a 400km/h run in one with 368kW leaves me in absolute awe.

This is a car, had it ever reached production, that would have undoubtedly rewritten the supercar hierarchy. You can bet there were a good few Italians relieved when Mercedes-Benz decided not to cash all those cheques and keep the C111 in-house.

Even unsold, the C111’s technical legacy remains impressive and every Mercedes-Benz on the road owes a little bit to it. No experimental car since has ever been so evocative, or iconic.

Indeed, if Mercedes-Benz pulled the covers off one at Frankfurt this year the reaction would no doubt be much the same -- if anyone carried chequebooks anymore, that is.