Jaguar XKR-S

What is it?

The quickest ever version of the XK – and the fastest Jag since the XJ220 supercar. Most of the extra pace comes from a special ‘driver focused’ chassis, developed by XK chief engineer Russ Varney and driving guru Mike Cross.

In the manner of many of the best performance cars, the XKR-S is a ‘skunk works’ project conducted by senior engineers around other projects – and which Jaguar’s management green-lit when they discovered it was so good.

The good news is that there will probably be versions of other Jaguar models similarly aimed at the keenest drivers. The ‘S’ sticks with the regular XKR’s 4.2-litre, 420bhp supercharged V8, mainly because the investment needed to raise the power would be prohibitive (and there’s a 5.0-litre V8 coming soon). However, ditching the electronic speed limiter lifts top speed to 174 mph.

What’s it like?

In a word, brilliant. A bald description of the mechanical changes doesn’t really do justice to the job; it’s the subtlety and judgement exercised on the way to the improvements that make the car so good.

The standard XKR is already a superb driving appliance, and the S gains firmer springs, dampers and anti-roll bars, steering is 10 per cent quicker and the ride height has been lowered by 10mm. It also gets race-bred brake calipers that not only improve stopping power but also reduce unsprung mass.

Styling tweaks include newly designed forged alloys that allow the fitment of yet-wider Pirelli P-Zero tyres on the rear. The package is topped off with a fairly discreet body kit which cuts drag by three percent, but makes major improvements to stability above 150 mph: lift at the front falls by 60 per cent, that at the back by 20 per cent.

On the road, the car has such built-in precision and body control that it’s a major surprise to discover that it rides well, too. The impressive structural rigidity, and aluminium construction, make the car very quiet over bumps.

The ride is firm, but beautifully controlled. Few keen drivers will be bothered by the relatively small comfort compromises needed to reap such benefits in steering feel, cornering grip and handling.