The XJR shares with the Le Mans-winning 1928 Bentley Four-and-a-Half-Litre a supercharger and a character that is emphatically and eccentrically British. Its sensuous bodywork hints at silken muscularity, while its leather interior looks as inviting as the idea of a Sunday afternoon by the fire. Like most luxury saloons, it promises comfort and speed, but what marks this car apart is the suggestion that driving it will engender a particular feeling of well-being.
Just as its subtly aggressive demeanour suggests, performance of memorable potency is duly delivered. Coupled to an automatic transmission, the cat will leap to 60mph in 6.6 seconds and, not very long after that, broach 155mph. Equipped with manual transmission, if you are prepared to endure the bothersome task of actually changing gear aboard this luxury saloon (and few owners will be), it will bound to 60mph in a lightning 5.9 seconds. And that, should you be wondering, is Ferrari-fast.
The XJR achieves all this through the ministrations of a supercharger which, in simple terms, is a bloody great pump that force-feeds the engine its combustible diet of fuel and air. The American-made supercharger is belt driven by the engine, and generates 10psi of pressure, relatively modest for such a device, but sufficient to swell the standard car's 249 horse corral to 326bhp.
More impressive still is a torque figure that burgeons to 3781b ft compared to the 2891b ft of the ordinary engine.
Yet it delivers its speed with subtlety, so much so that it is sensible to glance at the speedometer frequently if you're not to garner a starring role on Gatso films. Of course, you can hear the engine working at speed, the straight six issuing a lovelythrob at half effort, the supercharger overlaying this with a mild but intriguing whine. But, this Jaguar is quiet, its silence the main weapon fooling you into believing that you're travelling more slowly than you are. Comfort comes a close second. Following a far-reaching facelift intended to expunge the many irritations that beset cabin life aboard the previous generation Jaguar saloon, it is now possible for all but the most amply dimensioned drivers to settle comfortably, aided by a height trimmable seat and a tilt adjustable steering wheel.
I found myself switching gear just to challenge it, but always the ratios were exchanged with grace, delicacy and speed. The Jag's suspension is almost as accomplished. This is a big car, but it can be hustled along with unexpected facility. Really ambitious cornering will have the body swaying, but this isn't surprising in view of the car's bulk and its relatively soft springing.
The Jag's biggest flaw, however, concerns accommodation, or the lack of it. In theory there is room for five in this car, but in practice only four will ever be comfortable.
But that's the only major disappointment in a car that has been overhauled to exceptionally good effect. All of these XJs are vastly better than before, and all remain exceptional value for money. But the XJR is something really special.
SPECIFICATIONS JAGUAR XJR 4.0 £45,450 Engine: six cylinder, double overhead camshaft, 3980cc, 326bhp at 5,000rpm, 378lb ft of torque at 3,050rpm. Four speed automatic gearbox. Performance: 0-60 in 6.6 seconds, top speed 155mph. Fuel consumption: 23.4mpg.
COMPARISONS AUDI A8 £46,699 New age luxury saloon whose lightweight aluminium body improves performance and economy, though not hugely. Very roomy, elegant interior, and plenty of equipment as standard. Four-wheel drive provides terrific high-speed security and sound handling, even if it is not as wieldy as the Jaguar or BMW M5.
Despite 300bhp from a 4.2 litre V8, it is outsprinted by both, but does well given that it is designed to deliver luxury rather than the ultimate sporting drive. Undermined by a knobbly country road ride, but an imposing, appealing machine none the less.
BMW M5 £52,480 A bit of an old stager, but none the worse for that. Massive power, massive wheels and massive brakes ensure a sterling experience for the keen driver, who will enjoy searing performance and near-race car handling. But at a price: this caris significantly more costly than the Jag, and a few options will easily tip it the wrong side of £60,000. For the enthusiast driver, the better car, but, compared to the Jag, its interior is a little cold and antiseptic. Beginning to look dated now, too.