Today, I remember thinking as we purred westwards in the new Continental Supersport, may turn out to be a very bad day for Bentley.

We were in Spain, an hour out of Seville, heading for a circuit called Monteblanco to test the fastest, most powerful Bentley in history. It suddenly struck me that the Crewe company was taking a serious risk with its reputation, given that it was planning to let us loose on the very same asphalt we'd recently used to drive Jaguar's brilliant XFR at the limit. How would it look if a $265,000 luxury coupe couldn't match the all-around ability of a Jaguar sedan costing $97k?

A familiarization tour of the track gave little reassurance. It's a modern track, wide and well surfaced, with a very long straight that piles you immediately into a complex hairpin – ideal territory for a 621hp, 2.2-ton Bentley to attain huge speeds before overpowering its brakes and tires while trying to stop and turn at the end. As for the rest of the circuit, it's a succession of late-apex swoops – perfect for the Continental to demonstrate the traditional lack of adjustability of all-wheel-drive cars by negotiating them in moaning understeer. Despite the fact that I'd briefly and successfully driven the Supersports back in the UK, I had feelings of foreboding…

The Supersports itself looked wonderful. Derived from a "skunkworks" project produced under the radar by a group of Crewe car nuts who believed there was room for one more performance level above the Continental GT Speed, the model looks far sportier than any other Bentley model. All of the traditional chrome is replaced by "smoked steel" brightwork, the instant sign of a no-nonsense character. A modified front facade provides bigger intakes for cooling air, and there are new hood slots to allow the air out. The car wears a superb set of black, 20-inch, thin-spoked alloy wheels, through which its standard 420mm diameter carbon ceramic brakes, the biggest on a production car, are visible. They are fitted with specially formulated 275/30 Pirelli P Zero tires. The rear wheel arches are flared to cope with an increase in rear track, which engineers demanded as a means of adjusting the handling balance.  

It takes a whole suite of subtle engineering changes to a Speed to make the Supersports. The extra engine cooling air gathered at the front feeds larger chargecoolers that help lift the turbocharged power of Bentley's mighty 6.0-liter W12 by 3.5 percent to 621hp at 6000rpm, while also boosting torque by 6.5 percent to a new and extraordinary peak of 590lb ft, measurable anywhere between 1700 and 5600rpm. The car can now accelerate from 0-100mph in just 8.9sec and top 204mph, and it'll do these things whether it's burning pure gasoline or E85. Like every future Bentley, this Supersports will run on gas or ethanol, or any mixture of the two, and the driver won't be able to tell the difference. This is Bentley's highly original contribution to cutting greenhouse gas emissions by up to 70 percent.

The six-speed ZF paddle-shift auto now has a special Quickshift facility that halves gearchange times and allows the 'box to drop two gears at once under hard acceleration. The four-wheel drive system is biased to send 60 percent of the car's mighty torque to the rear wheels, making the car feel gently rear-wheel drive, while having amazing traction. The air suspension – whose rate the driver can adjust from the dash, but which also compensates automatically for rough roads or hard driving – has been re-rated to be a little firmer across the range.

The ESP has been tuned to allow for more exuberant driving before it intrudes. The carbon brakes, optional on other Bentleys, are standard on this one. The new set of thin-spoke forged wheels are specially styled to expose the brakes more and contribute 20 pounds to a total weight saving over the GT Speed of 243 lbs (the Supersports' carbon-tub bucket seats contribute 100lbs). There is no rear seat, only a big-diameter carbon brace running across the car behind the front buckets. All these changes go to make a model that Bentley describes as the most extreme in its history, which is why Crewe has applied the revered "Supersports" tag to it. The original Supersports was a Le Mans-spec 3-Liter that produced 85hp and could crack 100mph, in an era when most cars had 15hp and couldn't do 40mph.