THE Jaguar XJ range is readily acknowledged as one of the world's most technically-advanced cars and in 4.2-litre R form it certainly adds tingle to the sophistication.
There's 400bhp at work here from the V8 supercharged engine, along with 408lb/ft of pull, propelling an aluminium-structured, and thus comparatively lightweight, car - 1,659kg.
You will, therefore, not be surprised to learn that the XJR is some goer, electronically limited to 155mph and getting from standstill to 60mph in a push-you-into-your-seat five seconds.
What may well impress you is the manner in which the car deals with all this, totally poised and relaxed in its handling and as polished and comfortable in its ride as you could wish for.
Add in a range of highly-effective noise elimination measures and the sort of occupant-comfort devices that come in a £60,000 plus car and you have a combination of luxury motoring and 'oomph'.
Jaguar further refined the design for 2006 but it is what you don't see that really makes the car impressive.
Star of the show for me is the electronically-controlled air suspension, working with Jaguar's computer-run dampers system. At speed, the car lowers itself to provide crouched stability, while it virtually ignores road imperfections.
Notorious ridged concrete surfaces neither disturb the cabin comfort nor intrude much in the way of drumming. Full marks then for the bonnet lining, airtight seals, double-skin bulkhead and acoustic laminated glass.
Stability and traction control are among the driving aids, while the improved braking system deserves an honourable mention, wonderfully effective and effortless. Taken in company with the accelerator, you could drive the XJR in carpet slippers.
The pedal positions can be adjusted and there's electronic variation of the steering wheel height and reach. In addition, the front seats adjust electronically in just about every way possible, so that, in combination, drivers of any size and shape are catered for. The actual seats are in R sports leather, heated and with three-position memory.
Other XJR features include cruise control with autospeed limiter and alternative voice control for the automatic climate system, Bluetooth, satnav and the 12-speaker sound system. You get the comprehensive picture so I won't bother you with a list of lesser gadgets.
Given all this, it's disappointing that the cabin looks, well, so ordinary. There's leather aplenty and bits of chrome, and yet and yet. Possibly it's down to the new use of aluminium facings as standard, which doesn't seem quite Jaguar. Happily for traditionalists, you can have wood as a no-cost option. Ask for it.
As for space, the XJR provides plenty of roominess for all four occupants, but the boot is right in line with Jaguar tradition. On paper, 470 litres looks pretty good, but the shape is poor and a load of luggage presents a challenge.
Mechanically, though, the XJR is most accomplished - and I forgot to mention the silky six-speed automatic transmission - and, considering the engine power, economy is quite reasonable. The open road, where the car is right at home, gives you 31.4mpg and I averaged 25.7mpg over the week.
Other running costs aren't so good and the price tag itself is daunting. But the XJR remains a real and impressive treat.
FAST FACTS
Jaguar XJR 4.2 Supercharged
Price: £59,540
Mechanical: 400bhp, 4,196cc, 8cyl petrol engine driving rear wheels via 6spd automatic gearbox.
Max speed: 155mph
0-62mph: 5.3 secs
Combined mpg: 23
Insurance group: 19
CO2 emissions: 299g/km
BiK rating: 35%
Warranty: 3yrs/ unlimited mileage, 3yrs paint, 6yrs anti-rust