It’s just possible that this new Jeep Grand Cherokee SRT-8 is the most politically incorrect car you can buy. It is much more than just another overweight SUV. Its carbon dioxide emissions are so high that if you took it on a two-week 2,000-mile holiday to the south of France and back, the CO2 pumped out would weigh more than a family hatchback. And it will get through the unleaded quicker than a Rolls-Royce Phantom.

Can this be justified because it’s an effective go-anywhere family hold-all? Er, no. It will seat only five, the rear seat is cramped, and despite the fact that it’s a four-wheel drive, the people at Jeep are specific that, contrary to every appearance, this is not an off-road vehicle and should under no circumstances be used as such.

So not only is it one of the most polluting, profligate cars, it appears to be among the most pointless too. It is, however, better than anything else at one thing. And that is a redeeming quality that forgives everything else. The Jeep excels at the just and noble cause of wiping the smiles off the faces of Porsche Cayenne drivers.

Imagine that you just splurged £81,565 on a Cayenne Turbo S because you believe it’s the quickest SUV the world has known. And you pull up alongside this Jeep with its Carlos Fandango wheels and chrome-finish body mouldings. You feel sorry for the poor chap but a little annoyed too: as he blips his V8 engine, you can’t help but notice it sounds a whole lot better than yours. So you decide to show him.

The lights go green and off you thunder, but as you look smugly in the mirror to see the Jeep choking on your fumes, you realise it’s not there. In fact it’s alongside and, if your eyes do not deceive, it’s starting to pull ahead.

To top it all, the Grand Cherokee SRT-8 is less than half the price of the flagship Cayenne. It costs £40,585 and for that you get a snarling V8 motor with a 0-62mph time of 5sec flat. This is one of the legendary Hemi series, breathed on by Jeep parent Chrysler’s street and racing technology department, hence the SRT moniker. The engine displaces 6.1 litres and develops 420bhp. It’s shovelled under the bonnet, leaving no room for a low-ratio transfer box — just one reason why off-roading would be a less than good idea. The driveline has been reconfigured so that at least 90% of the engine’s power is fed to the rear wheels in normal driving.

Cosmetically there are extended sills, big bore tailpipes and those wheels. Inside you’ll find sports seats and aluminium highlights. But this Jeep is not just about big power and big looks, the SRT boys have tried hard to make it go round corners. Indeed Jeep claims its real home is the racetrack and points to its lowered ride height, stiffened springs and uprated antiroll bars to prove it. Moreover it also has some of the largest brakes I’ve seen on this kind of car.

The result is an SUV that’s been made astonishingly capable in the corners: I drove one round the Donington race circuit, a place where you’d think such a large SUV would be as at home as an elephant on an ice rink. Yet instead of falling over in the corners and wandering off to its spiritual home on the grass, it gripped hard, changed direction quickly and accurately and performed about as well as you’d expect for any car weighing 2Å tons.

Why becomes clear only on the road, where it appears to have no suspension at all. I drove along B-roads like I was crossing a minefield, jinking around potholes before those vast 20in rims crashed in and set off what sounded like a series of small explosions in the car.

But if you hunt out smoother, quicker roads, it’s an accomplished high-speed tourer. The gearbox may have only five speeds, but with so much torque you rarely need it to change. A squeeze on the throttle is all it takes to send the speedo soaring. And while the cabin is a mess, the driving position is commanding and the view imperious.

There’s no escaping the truth: the SRT-8 is flawed, pointless and reprehensible. I liked it.

VITAL STATISTICS

Model Jeep Grand Cherokee SRT-8
Engine type 6063cc, V8
Power/Torque 420bhp @ 6000rpm / 420 lb ft @ 4800rpm
Transmission Five-speed automatic
Fuel/CO2 17.2mpg (combined cycle) / 388g/km
Performance 0-62mph: 5sec/ Top speed: 152mph
Price £40,585
Verdict Unforgivable but not unlovable
Rating 4/5
Date of release On sale now

THE OPPOSITION

Model Porsche Cayenne Turbo S £81,565
For Huge performance, handles well for SUV, quite refined
Against Huge thirst, awful ride, terrible looks

Model Range Rover Sport Supercharged £58,045
For Characterful engine, attractive cabin, capable off-road
Against Aggressive looks, limited performance in this company