by Mike Collier

How do you improve on what is already the best car of the year? Easy - you supercharge it. By common consent, Jaguar's latest XK is its best sports coupe since the hallowed E-Type was finally regulated out of existence.

The XKR is the very top of the range model, adding a supercharger and more than 100 horsepower to the standard XK, while cutting the 0-60mph time by a second or so.

The XK is so good itself, that one might ask why an even hotter version was required.

The answer is simple: rivals such as BMW and Mercedes offer high-performance variants using their M and AMG badges respectively, and by adding the R to the XK, Jaguar can provide a viable and extremely attractive alternative.

Instead of buying an XK and adding options, customers for whom money is plentiful can go straight for the XKR with all the trimmings and still undercut the opposition.

Visually, the XKR is only subtly different to the XK. Bonnet louvres, quad exhaust pipes and a reworked grille are the items to look for, but the changes are perhaps less pronounced than many would wish.

With both coupe and convertible versions to choose from, buyers can get first-rate performance with or without wind in their hair. Interior design is essentially the same as the XK, but with range-topping upholstery and equipment as standard.

The XKR's greatest pleasure is not its elegant design but the incredible noise emanating form its quad exhausts.

The supercharger seems to concentrate what was already a terrific wail, adding a delicious rasp that is particularly noticeable when downshifting.

Many people rave about the noise Aston Martins and TVRs make, but the XKR is even more beautiful, as it seems more natural. Other cars may be louder and rortier, but none seem quite as satisfying as the XKR.

It's not all noise and no action, either. The XKR boasts impressive performance figures, yet no matter how enthusiastically it is being driven, it retains a languid, effortless character.

This is more of a sporting grand tourer than a hardcore race car, and all the better for that. It can be driven in a relaxed, almost absent-minded manner, as well as with a keen sense of involvement.

Requiring less technical skill to drive than the rear-engined Porsche 911, the XKR is no less enjoyable. In normal mode it is possible to waft smoothly across vast distances at the legal limit.

Selecting sport mode sharpens responses up, giving a more direct driving experience and even adding a little throttle blip when changing down through the excellent automatic gearbox.

One of the entire XK range's hidden delights is its clever boot. The tailgate encompasses virtually the whole of the back end - on a less streamlined car it might even be described as a hatchback.

Consequently, loading up is easy, even if the level of the boot floor is rather high.

Front passengers enjoy opulent appointments with beautifully-shaped seats and a large range of adjustment and decent legroom.

Though technically a two-plus-two coupe, the rear seats are really little more than large parcel shelves that even children would find a challenge.

Quite how a child seat for a ten-year-old would fit in is anyone's guess, though two Isofix positions are optimistically included.

For sheer driving pleasure, the Jaguar XKR is about as sublime as modern motoring gets, combining elegance with power and a good deal of class.

Few will be able to realistically afford actual ownership, but those that do will prove themselves to be connoisseurs of the rolling wheel with impeccable taste.

It is a fairly safe bet that this car will come to be viewed as a modern classic.