Top Gear drives the Jaguar C-X75

Thinking about it afterwards, another 2mph would have been nice. Because 2mph would have taken me to 186, which keen students of unit conversion will recognise as a nice round 300kph. The car certainly isn't the limiting factor, its big digital speedo's digits scrolling hungrily and dizzily away towards the maximum of about 220. But right now, 184mph looks like a big enough number to me. My mind is on matters other than arithmetic: it's streaming with rain, a corner is approaching - fast - and I'm driving a car that's precious and irreplaceable... albeit, I'm thinking, not as precious as my passenger and me. Time to get on the brakes.

Photography: Lee Brimble

This feature was originally published in the July 2013 issue of Top Gear magazine

We were always expecting - hoping - to be driving the C-X75 in different circumstances from this. And not only better weather (though you see it here in the sun at TG's own test track, for the big speeds I drove it at Jaguar's test facility at Gaydon). The company built five C-X75s to test and prove the technology and check this amazing hypercar was suitable for production. In 2011, the firm announced a run of 250 of them at a price of about £750,000. As a rival to the LaFerrari, McLaren P1 and Porsche 918, it'd have made a quarter of the very mother and father of group tests. But at the end of last year, part way through that development programme, in the tension of this four-way face-off of hypercar giants, Jaguar blinked first, concluding that in a fragile world economy there wouldn't be enough buyers for them all. The production car was, as the official coinage euphemised, "indefinitely suspended".

Jaguar could have quietly shoved the prototypes into a locked shed right then and walked away in hangdog embarrassment. But it didn't. There's so much technology in the C-X75 that its development continues virtually unabated, by a tight-knit team from Jaguar itself and Williams Grand Prix's Advanced Engineering consultancy division. Honestly, there's stuff in this car - electric motors, battery tech, electronics, composite construction, the astoundingly powerful and revvy combustion engine and more - that's not only more radical than what Porsche is using for the 918, but is, crucially, entirely relevant to Jaguar and Land Rover's future mass-production cars.

Does the fact that it's now a science project rather than a production prototype make it less interesting? The Saturn V rocket was a science project that added immeasurably to mankind's knowledge, and NASA never offered them for sale to the public and stopped building them after the 17th. That makes the five-off C-X75 look properly exclusive.

Can we agree it's the most beautiful of the hypercar bunch? OK, it's quite subtle as these things go. It doesn't jump out and ambush your eyeballs with outlandish proportions or a jutting forest of aerodynamic devices. Instead, it snares you more slowly and grips your gaze tightly and at length. There's no way it's retro, but it does have a Jaguar look. Design chief Ian Callum shrugs as he throws some light on why. "Jaguar aesthetics were born out of Malcolm Sayer's notion of aerodynamics. Unfortunately, it was a flawed notion."

Every single line and surface drips elegance and fluency, at least until you get to the back, where there's a honking great diffuser, which is all about purpose not beauty. There's also a rear wing with multiple positions for downforce and cooling, which at rest sits flush to the body so as not to disrupt the lovely curves of the car's hips and lower back. These things have been added since the concept car, but they didn't pain Callum. However, he looks at the wing mirrors as if they're a moustache on the Mona Lisa. "They muck up the design and cause noise, drag and turbulence." Worse was to come. "One of the hardest things of all was finding a legal space for a rear numberplate." Hmm. It's not all glamour in supercar design studios, then.

The scissor doors open into a cabin that doesn't ask you to bend to its will. You sit straight without having to crick your neck or distort your spine. In other words, Jaguar has resisted the temptation to chip away at the human-package space to make room for the engine, battery, motors, 14 radiators and all this car's bulky mechanical complications. And yet Jag has still kept kith-and-kin close to the look of the original 2010 Paris show car, the machine everyone clamoured that Jaguar go right ahead and build.

Everyone quietly ignored the fact that the concept car - jet-powered, you might remember - was hardly a well-grounded exercise in packaging feasibility. Or any kind of feasibility, really. Alister Whelan, who created the concept along with Matt Beavan and head of advanced design Julian Thomson, was given the job of protecting it into production.

Having harnessed the grand prix team's aero expertise, the final car respects aerodynamics as any 220mph car must, both in terms of air going around it (for drag and downforce) and air going through it (for cooling). The aero guys were given almost no freedom by Ian Callum's team on the visible parts of the car - apart from that rear diffuser. But underneath, and around the engine bays and within the cooling pathways, they were allowed to fill their boots. Talking of boots, there isn't one. You want a shape this slinky and you want it to fit an engine, two electric motors, a battery, a fuel tank, 14 radiators, inboard bell-crank suspension, a habitable cockpit and a boot? Getouttahere. People with £750,000 cars can employ someone to go ahead with their personal effects.

There are comforts among the cabin's striking simplicity. The multimedia screen is the usual one on top-end Jags. The climate control is operated via the nice bank of switches out of the F-Type. The transmission selector is a simple series of buttons: PRND, a cloak of simplicity over the dizzying complexity of the mechanism it controls. The TFT-screen virtual instrument cluster shows battery and fuel state and subsidiary info, plus a digital speedo clear enough, as I've proved, to be read in a hurry. There's also a large rev-counter and a power meter.

Jaguar and Williams started the project with the following four simple but wildly contradictory goals. The looks of that Paris concept. The performance of a Veyron - 0-62mph in 3.0secs, 0-100mph in six. The pure-electric range of an Ampera/Volt - 40 miles. The official-cycle CO2 of a Prius - 89g/km. Other than that, because they realised jet turbines were, for the moment but not indefinitely, out of the question, they had complete engineering freedom. Beyond the steering wheel, that entertainment screen and the aircon controls, there's hardly anything bigger than the nuts and bolts that's lifted from any other Jaguar. Any other vehicle with numberplates, for that matter.

So they ended up with a 500bhp, four-cylinder, 1.6-litre engine. It's a blank-sheet job, not derived from a road or race unit. Up to 5,500rpm, it's supercharged. After that, it hands on to a turbo, which keeps going to the limit of 10,200rpm. That is not a misprint. Meanwhile, there are two electric motors: one at the rear feeding through the seven-speed gearbox, and another at the front. They make almost 200bhp each. And 300lb ft of torque. Again, that's per motor. This is a six-seconds-to-60mph car, even before the engine has started.

I get a few demo laps around the snakier bits of Jaguar's Gaydon track in electric mode. The thrust is eager and true. Such is the rpm range of the car's special motors that it never needs to shift: the rear motor stays in second, and we're good for nearly 100mph. Because the front motor is at a fixed gear about equivalent to sixth in the rear, you have a significant natural torque bias to the rear, though vectoring (switched out at the moment because calibration continues) could alter that if needed. Anyway, there's loads of traction, even in the wet.

But when the engine does start... oh, my. We switch to a different prototype, one without such a pretty paint job but with a roll cage. It's the one for hard use.

The engine sounds like a superbike's does at low revs: rattly, like it's ingested gravel, but eager on the exhaust. There's barely any flywheel effect, partly because it has no starter or alternator or aircon pump or power steering pump attached. This allows it to be razor-sharp on the throttle, but it also makes it a bit jangly around idle. Indeed, driving at the suburban speeds around the track access roads, it feels and sounds coarse, with gravel hitting the carbon-fibre tub and the sharp-edged engine and gearbox effects.

Jaguar's head of set-up Mike Cross takes me for a couple of circuits of the infield course. Oh, good grief. Several corners are inches deep in water, and it's a channel of Armco only a couple of car-widths wide. The car's traction is strong, and the torque bias is clearly still to the rear so that power slides are repeatedly on. But I'd rather drive it where there's more room for error, so we swap places and I head to the big airfield-runway-based track.

One of the really nice things about this car - one of many characteristics it shares with the Porsche 918, in fact - is the driving position and subsequent visibility. You're not scrunched up like a hostage or semi-blindfolded. You can operate your limbs comfortably, and there's enough vision. The topography of the wheel-arch humps isn't only handsome, it gives you a good reference about where the car is on the road.

An exploratory lap finds power that's immense but not quite savage. Cross encourages me to use the revs. Swinging it up through 5,500rpm in fourth, where the supercharger declutches and the turbo takes charge, there's no step in the delivery. But anyway, the rear e-motor alone makes more torque than the engine at its 6,600rpm peak value. Having verified how this feels for the sake of interest, there's no reason to drop below about 7,000 anyway, not once we're on the big track. By this time, the engine sounds wonderful and hair-raising, flying up beyond 10,000, then accepting each upshift with a bang in your back.

There's no delay, just a simple serration in the acceleration as each gear is switched. It's a bespoke single-clutch transmission: a twin-clutch would have weighed significantly more, and its extra bulk would have interfered with the airflow through the rear diffuser. Oh, and there's no reverse gear. The engine simply declutches and the motor current is reversed. When I'm driving gently around the track access roads, gearshifts make your head nod, but there's a potential fix in programming the front motor to fill the torque hole.

Back on the track, after I've done a couple of laps, Cross reaches over and presses a button, confirmed by an innocent little flashing LED. This is what he calls "full-fat mode". Now the electric system gives its absolute all, even if it means borrowing performance from the future: it depletes the batteries so you'll be a bit slower later until they've recharged, either by plugging in or driving more moderately and using spare engine power to recharge.

Here's the savagery. Out of corners, hauling up the straights, the whole effect is significantly emboldened. The type of acceleration, the shape of it, isn't greatly different, but the magnitude is amplified. Barrelling up the straights etches itself deeper into the memory, and slowing at the end becomes a job that demands more insistently that you don't mess up.

The chassis is terrific. Yes, at urban speeds, the stiff springs make it pretty hard, but you can always feel the body is reassuringly rigid so, as you get some speed into the suspension movements and the inboard dampers begin to do their work, you notice the precision. It rounds off sharp impacts and breathes nicely over dips and crests. At speed, the aero pushes you into the track and reassures you by tightening everything up.

But, best of all, is the steering. Its calibration of weight and directness is spot on, both for easing into fast arcs and for bigger forays into the lock for tight bends. And even if the assistance is electric, there's plenty of road feel, so as the car begins to drift out as it hits a light crest or a slipperier patch, you're kept in the loop. That's a lovely characteristic in a fast car on a wet day. There's no significant understeer. As a matter of fact, with much throttle on, things tend to gentle oversteer. But every time it pays me a visit, its warning and progression help me out.

And all this is the fundamental chassis we're talking about, without any overlay of electronic gizmology. There's an e-diff on-board, and there's the possibility of torque-vectoring front to rear. Williams's chassis engineer Simon Newton has been separately calibrating them, but he doesn't want anyone to try them until he's settled the voodoo of making them work to reinforce one another. Once again with the C-X75, research continues because it's useful to Jaguar as a whole, not just this car.

To get back to the full beans for a second stint, we come in to hook the car up to its charger - a humming three-phase 20kW contraption with a cable like a ship hawser that'll fill the battery in just 40 minutes. A good time to talk to Paul Newsome, project head, about why they selected the balance of engine power, electric power and battery size. At one extreme, couldn't they have just stuffed the V8 in there and forgotten the rest? "I can confirm the V8 won't fit," says Newsome before the question has fully left my lips. But anyway, a modern supercar needs sensible economy. Not the ridiculously artificial economy of the official test and its CO2 result (these ignore energy taken from the grid and the CO2 that stems from it), but enough economy to give decent driving range. To get that, some engine downsizing was important. But that tends to mean a combination of low torque and/or turbo lag. So it's sensible to add electric motors, not just because that gives you hybrid-fuel-economy benefits, but for their instant response, amenability to high-finesse traction-control systems and four-wheel-drive ability. OK, so how much electric power to give the system?

Newsome says they modelled a whole range of balances of electric to piston power, with various battery sizes to boot. He decided on 500bhp from the engine, so that, even after using up the batteries in full-fat mode, there'd still be enough combustion power for a sustained 190mph top speed ("We thought about where there were roads in the world that you could use all the performance and for how far"). But the batteries and motors are something special, and they give the system the flexibility and power it has. First, the little axial-flux motors, which can produce several times more power for their weight than a conventional motor, and have a wider operating range too. They're each just 22kg for their 200bhp and 300lb ft, and not much bigger than a round washing-up bowl. So the car could use lots of electric power. Second, they wanted to use a high voltage because it's more efficient, settling on 600V. As the voltage is proportional to the number of cells, that pointed to a big battery. They got a 19kWh unit, mostly packed down the central spine of the car. It uses the same power management and cell chemistry as a Williams F1 battery, and so its power density is about halfway between existing road cars' and a grand prix car's. Having got the battery they needed for the power they wanted, it turned out the electric-only range was just what they were wanting too.

"We aren't just delivering a supercar, we're developing real-world technologies," Newsome says. Indeed. These axial-flux motors are a huge step ahead. So are the electronics and their cooling: instead of using heat sinks into conventional water-based coolant, the coolant is non-conducting, so it can be passed directly through the electronics without shorting it all out. The effectiveness of that cooling means the battery and motors can run at full power - nearly a quarter of a megawatt, don't forget - for sustained periods. Then there's all this downsizing tech on the engine. Remember, Jaguar Land Rover is presently building a giant factory in Wolverhampton to make four-cylinder petrol and diesel engines. They might not boast 500bhp, but they'll still have healthy performance and strong economy, thanks to findings from the C-X75. And with one of these electric motors between them and the gearbox, they'll answer the accelerator pretty smartly too.

One more thing. The carbon-fibre structure of the C-X75 isn't a one-piece thing like a 918's or a McLaren's. Those use a process called resin-transfer moulding because it's relatively cheap and can be made in high numbers. The Jag was designed to be made from panels and sections of compression-moulded carbon fibre, a technique from Williams. Uniquely, such carbon parts can be easily incorporated, says Newsome, into an aluminium body shell. Who's the world leader in aluminium body shells? Jaguar Land Rover. Just saying.

The decision to kill C-X75 production must have felt to Jaguar like strangling a puppy. But there simply weren't likely to be enough buyers for this and the Porsche and the McLaren (and there still aren't, even if Ferrari, characteristically, is exempt from such struggle). But the fast-track engineering it embodies will certainly live on in hundreds of thousands of people's Jaguars and Land Rovers. In very, very few years from now. But even so, right now I'm very sad that we'll never be given the chance to have our day brightened by the sight of its wonderful shape gliding by, or experience it disappear in a vision-blurring, ear-splitting testament to the new-world power it embodies.