Those with longer memories may well remember a time when a Jeep Grand Cherokee was one of the big hitters in the luxury 4x4 class. Admittedly this was a time when the luxury 4x4 class consisted of the Jeep and the Range Rover, but that's not important right now. The Grand Cherokee was something special, a mould breaker. Since then, a whole host of new entrants have queued up to work the big-hearted Jeep over but with the mighty 6.1-litre SRT-8 model, payback time may have arrived.

Let's have a brief recap. When the Grand Cherokee debuted in late 1995, many UK journalists were a little puzzled. The 4x4 market was just fragmenting with the introduction of cars like the Toyota RAV4 and many tried comparing the Jeep to far more agricultural fare such as the Land Rover Discovery, the Isuzu Trooper and the Mercedes G-Wagen. With an on-road ride that was unheralded at the time, the Jeep could really only be compared with the Range Rover, and in making a big 4x4 with a tarmac bias - although a company with an off-road heritage like Jeep would never admit it - the American manufacturer had started something. For a couple of years, the Grand Cherokee was the hot ticket with soaring residual values and a sky high image. Then cars like the Mercedes M-Class, BMW X5 and Lexus RX300 arrived and the Jeep found itself battling among the relegation places.

"Show this Jeep a wet grassy slope and it'll likely be spinning its wheels impotently. It'll sound great doing it though?"

The latest version of the Grand Cherokee, introduced in 2005, sees something of a return to form, but it's never going to be enough to challenge the very top end Mercedes MLs, Range Rover Sports, Porsche Cayennes and Volkswagen Touaregs. Instead, Jeep must set its sights a little lower and concentrate on putting a good working over on cars like the Land Rover Discovery, Toyota Land Cruiser and upscale BMW X3s. It's still a tough task, but the Jeep has a couple of secret weapons up its sleeve. The first is the best diesel engine in the class in the shape of the 218bhp 3.0-litre Mercedes derived common rail unit seen in the Grand Cherokee CRD. The other is the engine we look at here, the 420bhp Street Race Technology (SRT)-fettled eight cylinder behemoth costing £41,190.

No doubt there are some die-hards who will find the idea of a Jeep with twenty-inch alloy wheels, performance tyres, a low front spoiler and ninety per cent of its drive directed to the rear wheels more than slightly sacrilegious. Show this Jeep a wet grassy slope and it'll likely be spinning its wheels impotently. Console yourself with the fact that it'll sound great doing it though.

You won't mistake this model for any other in the Jeep line up. In fact, it's probably the meanest looking 4x4 money will buy. The centre-mounted dual exhausts would look more at home sprouting out of a Lamborghini Murcielago and the sound the Jeep makes when at tickover is not dissimilar - a truculent, bass tone that will frighten small children. Pop the bonnet and you'll see the same 6.1-litre Hemi engine that's shoehorned into the Chrysler 300C SRT-8 and also its US cousins, the Charger and the Magnum. In the Grand Cherokee, peak power arrives at 6,000rpm and the 420lb/ft of torque presents itself for inspection at 4,800rpm. That's comfortably more than a BMW M5, in case you were wondering.

Drive is directed largely to the rear pair of Goodyear Eagle 285/40s via a five-speed automatic gearbox. Torque to the front wheels varies between ten and one hundred per cent, depending on grip levels, but in 'normal' driving situations fully nine-tenths of that power goes aft. Somewhat refreshingly, Jeep have ditched any pretence of off-road ability and have even dispensed with the low Range gearbox seen on other Grand Cherokee variants. The reason why the SRT-8 isn't fully rear-drive is that the company wanted to maintain an element of all weather performance.

So, we've talked about this engine enough. What'll it do? This is where it gets fun. Dial in a bunch of revs and sidestep the footbrake and you could well replicate Jeep's figure of 5.2 seconds to 60mph with the good ol' quarter mile being dispatched in 13.5 seconds. Drive like this and you'll see single figure fuel economy returns but a more measured right boot will acheive around 15mpg. All that go is no good without an element of control and Jeep have worked hard to keep this 2,180kg monster manageable. The uprated four-piston Brembo brakes grip massive 360mm front discs and guarantee some serious retardation power with a stop from 60mph possible in just 36.6 metres.

Likewise, there's been a lot of work done on the handling package. Bilstein shock absorbers and an industrial-grade strut brace under the bonnet team up with stabiliser bars for the independent front and live-axle rear suspension. Jeep have engineered a rather firm ride into the vehicle and have also fitted deep bucket seats so that front occupants aren't launched sideways by the g-forces this model can generate. Slalom performance is said to be the equal of a Porsche Cayenne Turbo with superior acceleration to the German car when the road opens up.

Respect is most certainly due to the Grand Cherokee SRT-8. The biggest hitter on the 4x4 block, it's not difficult to imagine that this vehicle will have a significant 'halo effect' for lesser Grand Cherokee models. Its niche may be small, but the SRT-8 has managed to put a sound spanking on a bunch of far pricier pretenders.