The R is the most powerful Jaguar saloon ever, with the creamy smooth 4.2-litre V8 engine force-fed intercooled air via a supercharger bolted on top. Add in a six-speed ZF automatic gearbox, re-engineered sports suspension, race-bred Brembo brakes and the latest incarnation Computer Active Technology Suspension (CATS), and you have a British bruiser to take on the fierce BMW M5.
Except with its automatic box, sporty yet comfy seats, and newer, better, plusher interior you have a car that will cruise benignly and with no fuss. All very easy and relaxing. 'My mum could drive this', you think.
The dash has the same Jaguar horseshoe as the X-type, and has much more character than the old car. There is also a fancy new electronic parking brake that switches itself off when you start moving. I like the seating position, which adjusts massively, including the pedals.
What a fine car, I thought, as I pottered out of town. But come the open road, floor it and, like the Millennium Falcon entering hyperspace, the world goes fuzzy. All I remember was a piercing ghostly howl of the supercharger, and me thinking 'I should probably stop.'
This car is so fast. It does 0-60mph in 5.3 seconds and tops out at a limited 155mph. But because the gearbox zips up between gears imperceptibly, all you get is constant, incessant, violent acceleration forever. And that intoxicating howl.
Manual cars like the M5 might be quicker in a straight line on paper but for real world users the automatic S-type R is miles faster. With six gears, there is none of that irritating searching you get on lesser 'boxes.
And it rides beautifully, while providing fun at the corners as the steering is sharp without being fidgety. It will slide but the Dynamic Stability Control always masters it after letting the car show off a little first.
It has CO2, mpg figures and all that fleety stuff, but they're in the fact file below - if you are thinking of having one of these cars, such figures are all bit meaningless.
The S-type R is all about performance, and it has got it in spades. It is understated, beautifully built and super quick. And it sounds amazing.