Exclusive: driving the revolutionary Mercedes C111 concept

Matthias looks nervous. He gives the outsized three-pointed star a paternal little pat. A nervously paternal little pat.

"So, erm, how much is it worth?" I ask, motioning to the orange-over-black mid-engined wedge with the elongated anteater nose that is clearly his pride and joy.

Pictures: Richard Pardon

"It's very difficult to say," Matthias replies, chewing his bottom lip slightly, "because it is such a special car. But I know that it is insured for €6m."

That's £4.6m (Grexit notwithstanding) of ultra-rare, museum-grade Mercedes, on a week-long sabbatical from its cloistered, climate controlled Stuttgart home, and about to do battle with the heathen Surrey rush hour. It's like taking a Picasso or Gerhard Richter for a run through a paintballing stag weekend.

Although self-evidently a fabulous oddity, I doubt many folk have the faintest idea just how significant the Mercedes-Benz C111 really is.

If you know your concept cars, then you might recognise it as one of the flag-bearers for the particularly fertile period in car design that occurred at the fag end of the 1960s, when the curvy, glassy sensuality of that libertarian era morphed into the wedgy, experimental and ultimately more paranoid 1970s. Someone was definitely slipping something into the water supply.

The C111 actually straddled the eras. It first appeared at 1969's Frankfurt motor show, and its gullwing doors gave it immediate kinship with the 300SL, another far-sighted and uniquely doored Merc that had lit up the previous decade like a firework.

Typically for Mercedes, though, the C111 wasn't just corporate willy waving or a lysergic piece of designery indulgence. No, it was a fully functioning prototype, initially powered by Felix Wankel's clever engine, a revolutionary technology that replaced reciprocating pistons with parts that rotate in the same direction.

Nice idea, and one that would be successfully mass productionised by Mazda, but Mercedes soon walked away from it, cost and reliability travails outweighing the 280bhp, triple rotor's inherently smooth character and compact size.

It didn't deter the C111's evolution, though. In 1970, a further four were made, with various other versions emerging over the next decade, including groundbreaking turbodiesels and several record-breakers. In fact, a total of 14 would be made in all, marking this out not just as a lone concept car and more of an entire visionary family.

At some point in the early 1970s, Mercedes also slotted the silky 3.5-litre V8 used by its saloons into a C111, and asked ZF to design a bespoke five-speed gearbox for it. The body is fibreglass, glued and riveted to a steel chassis.

It's a runner, and Matthias is one of those hardy souls entrusted with keeping it that way. Today, TG.com is driving it. Not many people have had the privilege.

For a 45-year old concept car, the C111 really is remarkable. Car companies are forever offering us a quick spin in their latest show pony, but however glitzy the top half might be, the underpinnings are usually held together with sticky tape and glue, the resultant driving impressions done on a wing and a prayer. At about 10mph.

Not here, though. Those famous doors need to be open and closed carefully, but they're properly engineered. The interior feels as well screwed together as any period Mercedes, and even the air conditioning works properly.

The seats have a sturdy checked trim, the pedals line up properly with your feet, and the driving position is spot-on. The V8 fires on the first turn of the key, and immediately settles into an even-tempered idle. I know mass-produced moderns that are harder work than this.

First gear is on a dog-leg, and you need to push a little button nestled in the top of the gear-lever to access it. But the action is smooth, and the C111 pulls away without a trace of judder or anguished clutch. It's probably one of the most pampered cars on the planet but even so, it's almost ridiculously polite.

In fact, an unexpected issue soon arises. Although more than happy to chunter along, the C111 is clearly capable of going a bit faster. True to its experimental role, the car'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 amazingly well, its tall, old school tyres expertly riding the undulations and camber changes typical of Britain's malnourished B-roads.

I expect bits of trim to start falling into my lap as we dart around potholes, but the C111 stays solid and resolute. I can even confirm that it actually handles properly, an observation I didn't expect to be making half an hour ago.

As for Matthias... Matthias?

The C111 will be at this weekend's Goodwood Festival of Speed