Is the S-type R the perfect getaway car? In black, the average passer-by doesn't really acknowledge its existence. I did notice the occasional "in the know" person give it an admiring glance. The S-type R's non-supercharged brethren are classy-looking cars, even if the retro-style nose polarises opinion. The R version looks like it was hewn from a different, far sexier substance though. The changes are few enough, but effective: a wire mesh grille, integrated spoilers and those gorgeous 18-inch wheels. The Xenon headlights also add to the sportiness of the car, and recreate daylight very effectively. As I write this, the facelifted S-type is being revealed at the Detroit Show, and those changes further enhance the R version.

As a driving enthusiast, my only criticism of the S-type R Jaguar is the lack of a manual gearbox option. However, as an objective journalist, I acknowledge that the market for a manual version must be tiny, and the manual 'box used in the rest of the range probably is not strong enough to cope with the prodigious output from the supercharged V8 engine.

That engine is really the reason this car exists. I wonder did Jaguar really think they were going to create such a fabulous alternative to the BMW M5 when they decided to bolt a supercharger onto the 4.2-litre V8. The figures speak for themselves - 400 bhp peak power and over 400 lb.ft of torque. These numbers are translated into a 0-60 mph time of 5.3 seconds and a top speed limited to 155 mph. Try to remember that this is a four-door saloon that weighs nigh on two tonnes...

Really, the Jaguar S-type R is a rear-wheel drive, supercharged lesson in modern physics. It can't quite alter the rules, but it makes a good job of bending them into a shapely curve. Acceleration is rapid, but standing starts are not what a Jaguar saloon is made for. Effortless performance is, and the S-type excels; at any speed, there is meaningful forward thrust available. Even at silly speeds close to the limiter, the S-type R surges forward. To say that the Jaguar goes like a train would be inaccurate if the Train a Grande Vitesse did not exist. Throughout the delivery of this performance, the S-type is eerily refined; the huge tyres are the only source of unwanted noise, and even that is quite subdued. Wind noise is contained, and the engine itself never sounds raucous; at idle, the rumble is almost inaudible. The sound rises to a pleasing growl up to about 3,500 rpm, but put your foot all the way to the carpet and the characterful V8 sound is drowned out by the whine of the supercharger. The occasional person may not like this, but we did.

When you come back down to earth and realise that you shouldn't really be travelling as quickly as you are, the brakes are quite up to the job. The "R"-logoed callipers (by Brembo) grab the discs hard, and the pedal feel is just right. However, those pesky laws of physics get in the way again if you take liberties. Some fade is apparent after a succession of high-speed stops, but I must stress that I don't imagine the average owner would subject their car to this sort of abuse. The same comment could be applied to the B-roads we use to test the handling of the cars we review; though the S-type coped admirably with tight turn after tight turn. An all-out attack is stifled by the brakes, but the chassis itself is a gem, dealing with broken tarmac and yumps as if they weren't even there. The steering lacks a little communication, but is wonderfully direct, and the nose of the S-type changes direction remarkably well.

For research purposes we turned off the traction control for a couple of runs on our favourite road. The conditions were dry, but it was still very easy to light up the rear tyres. Exiting tight corners is huge fun, with oversteer available on demand, though the steering feel and sheer weight of the car will probably prevent you from exploring the outer reaches of the car's (and your) abilities. The lack of a manual gearbox doesn't help either. Saying that, the rear end proved wonderfully controllable in damp conditions if the car was held in second or third gear. With the reassuring traction control reinstated the fun does not stop. The rear end does slide ever so slightly before the electronics stop you putting it in the hedge, but it is not quite as nannying as say the New Labour government.

While all this hooliganism is going on, your passengers may be almost oblivious to it, such is the S-type's refinement. Nevertheless, the seat belts will be needed to stop them sliding about on the flat and slippery seats. Other than for that, the seats are superb, with a huge level of adjustment. Like the rest of the interior, they look good and feel of very high quality too. Away from a twisty road, they are comfortable. The S-type's forté is sweeping A-roads, where high average speeds are the norm, and dawdling traffic is soon dispensed to the sound of the supercharger. Motorways are incredibly dull; it feels as if you are not even moving in the S-type when travelling at the UK speed limit. This car is ideal for the frequent autobahn user, though we averaged only 15 mpg in the week with the car, which would make an expensive commuter car.

Do you know many people that commute to Germany though? Me neither. So who will buy the S-type R? It costs £48,613 at the time of writing. The E55 AMG Mercedes has more power, but costs a whopping £62,000. The same applies to the Audi RS6 to a lesser extent, at £58,000. BMW's forthcoming M5 could be a natural rival, though it is rumoured to have closer to 500 bhp, and that will not come cheap. The C32 AMG Mercedes has similar performance to the S-type, at £4,000 less, but it is a smaller car. The BMW M3 is "only" £40,000, but we don't think that the same buyer will contemplate a fast luxury saloon and an overtly sporting coupe. The automatic-only option hints at the likely buyer. Sadly, the Jaguar will be bought for its prestige and class first, and its astounding dynamics second. Whatever way you look at it though, it's a steal.