We’ve been teasing you about this car all week now, and we’re proud to present you this exclusive road test of the Jaguar C-X75 Hybrid Prototype. Driving’s David Booth is one of the very few extremely lucky souls in the entire world to have ever driven Jaguar’s rare C-X75, which isn’t even in production. How many of you knew what we were up to? It turns out that after we dropped our second hint, most of you clued in right away. Tell us why in the comments below, and enjoy the ride. Don’t forget to check out a video on the design history of the stunning C-X75.

GAYDON, ENGLAND — It’s difficult to know where to start, really.

Should I be trumpeting the impossibility of the original design challenge that had Ian Cluett, head of Williams Advanced Engineering’s powertrain development, charged with designing a car that was as fast as a Veyron (i.e. less than three seconds to 100 kilometres an hour), with the pure electric range of a Chevrolet Volt (60 kilometres) and the overall CO2 emissions level (Europe’s measure of fuel economy) of just 89 grams per mile?

On the other hand, the crucial fact could be that without much fuss, and your own Walter Mitty at the wheel, the Jaguar supercar screamed to 310 kilometres an hour on the (relatively) short straight on the company’s High-Speed Emission Circuit. It could be, I suppose, that during all this high-speed anarchy, the mid-mounted Williams engine — an-impossibly-small-for-this-much-power 1.6-litre four-banger — was howling like a maniacal BMW 1,000-cc superbike with an Akrapovic pipe. Or, wait a minute, the real news is that, despite its incredible complexity — an engine with both a supercharger and a turbocharger, two electric motors, two lithium-ion batteries, two electrical inverters and no less than 14 radiators — the darned thing, Jaguar’s incredibly exotic, impossibly sexy and sadly stillborn C-X75, is as easy to drive as an F-Type.

Welcome to the best car you — nor anyone else, no matter how rich — will never drive. Just the numbers alone astound. Top speed, on a day not quite as rainy as my drive, is significantly somewhere north of 320 km/h (the speedometer tops out at 196 miles per hour, or 313 km/h, but thanks to the Williams people, we are able to download real-life data from the F1-style telemetry systems). That’s in what Mike Cross, Jaguar’s vehicle integration engineer, calls “full phat” mode, with both 190+ horsepower electric motors and the super-revvy 502-hp Williams-designed gas engine all pumping maximum go-juice to both sets of wheels (the total, says Cluett, adds up to a maximum just shy of 900 horses).

Almost as impressive is that the C-X75 will accelerate to 100 km/h in about six seconds powered by electricity alone. That’s right, the C-X75 is faster than most cars on the road today before you even turn the engine on. Top speed, again in pure electric mode, is about 150 klicks an hour. Indeed, around something like Jaguar’s tight handling track, the C-X75 would prove as quick in pure EV mode as many a gasoline-powered sports car.

It will also, as per the design mandate, crawl along at more sedate speed for more than 40 kilometres (no one has really pushed the range limit yet, because the system, still in prototype development, is not yet optimized for battery depletion). But, in most of its EV/hybrid operation, the supercar is very similar to any plug-in on the market today. The battery — actually batteries, since there are two, saddle mounted on either side of the engine — are 650-volt lithium-ion and boast 19.3 kW-h. Like a Prius, the battery is never charged to its limits and once below 20% of capacity, it stops pumping power to the electric motors. And, again just like a garden-variety Toyota, the C-X75’s regenerative brakes recharge the battery when the free electrons start to get low.

What is different — and don’t those crazy Brits think of everything — is the Interior Sound Synthesizer, which is just a fancy name for an amplifier that vibrates the C-X75’s roof — yes, the whole roof — to produce engine-like sounds as you drive. As times, it sounds like a high-speed two-stroke motorcycle, other times like a thrumming turboprop airplane straining for altitude. Best of all, when it’s being charged by its high-speed electric port, the ISS emits a raspy low-frequency thrum, much like the sound effects Ridley Scott employed every time the alien was about to pounce on Sigourney Weaver. You half expect the whole car to pulse maliciously and snatch small children from the street. Even refueling, the C-X75 sounds like a menace to society.

In Cross’s “full phat” mode, meanwhile, it sounds like an angry, high-revving superbike, hardly surprising since the Williams-designed engine is a leftover from Formula One’s ill-conceived plan to power the world’s most exotic racecars with four-bangers. Though its 10,300 rpm redline is stratospheric by production car standards, it’s positively pedestrian by Formula One measure, the bottom end completely understressed even though it’s screaming like a refugee from the Nurburgring. Indeed, says Williams, the only thing stopping it from spinning higher and harder and producing even more power (502-hp from just 1.6 litres is an incredible 313-hp/L) is some F1-style pneumatic valves.

The rest of the technology beneath designer Ian Callum’s impossibly beautiful sculpting is also F1-like. Were I trying to simplify the explanation, I might say that the C-X75’s chassis is based on a carbon fibre tub much like McLaren’s MP4-12C, but, in fact, Jaguar and Williams have taken the alternative material design even further. Unlike the MP4, the Jaguar’s rear sub-frame is also constructed of carbon fibre (the 12C’s is aluminum). Indeed, Felipe Austin Bodely, Jaguar’s vehicle integration manager, won’t even call the rear section a sub-frame, preferring to think of the C-X75’s superstructure as two main frames bolted together by no less than 14 massive, M10 high-tensile steel bolts embedded in the carbon fibre molding. By comparison, the F1-inspired, lever-armed double-wishbone suspension seems almost pedestrian.

All of this, of course, had to fit under the skin of the original C-X75 (C for concept, X for experimental and 75 being Jaguar’s anniversary) concept car, which, if you remember, was powered by a miniature gas turbine engine. Making a production version of such a slinky silhouette, massaging it so real human beings could sit in it (the concept had fixed seats and minimal legroom)‚ and then finding space for the gas engine the original never intended was not without its challenges. Throw in the fact that there are those 14 radiators I mentioned earlier and you have a packaging nightmare.

The solutions were ingenious. The gas tank, for instance, is in the centre tunnel where a transmission would normally lie (the seven-speed manumatic is a transaxle) centralizing the mass near the C-X’s centre of gravity and having the added benefit of not affecting the polar moment of inertia as the fuel level recedes. Smaller wheels and a shallower rear angle of attack allowed Jaguar to lift the roofline (to fit helmeted heads) without raising the car’s overall height. Interestingly, Bodely says one of the toughest engineering challenges was fitting windshield wipers, the car’s incredibly low hood and dense packaging leaving very little room for yes-I-know-how-small-they-are wiper motors.

Indeed, the most amazing thing about the C-X75 is not its top speed (but, did I mention that I managed 310 screaming kilometres an hour in the wet, on a short straightaway, on my first lap) but its civility. In the final, most production-ready prototype (Number 5), the leather seats, the buttonry and even the touchscreen would be familiar to anyone who has driven a Jaguar of recent vintage. And, in terms of driving, the C-X75, thanks to its electric power steering, is no more difficult to manhandle than a F-Type. Even the ride is not supercar stiff.

But, make no mistake, this is a supercar and, assuming Jaguar develops it further, maybe the best supercar one could buy, again if the company reverses course and builds the proposed 200 examples. As it is, Jaguar says production is “indefinitely suspended.” Everyone I talked with inside the Gaydon engineering centre desperately hopes the C-X75 gets out of the penalty box.

“There’s still some hope,” says Callum with enough bonhomie that he almost manages to convince. Let’s hope he’s right; it would be a travesty if the C-X75 never made it to production.