Last month we covered the distinctly mad 165mph Cayenne Turbo, this month it's the turn of its brother, the mildly bonkers 150mph Cayenne S, offering 2245kg of real Porsche for just ΂£44,530; pound for pound (or should that be pound per kilo?) that makes the Cayenne S the cheapest Porsche on sale today. Actually, better make that starting price ΂£46,505, as you'll need to spend ΂£1975 extra on the optional air suspension (standard on the Turbo). The ride quality of the Cayenne S is pretty awful on the standard steel springs, competing head on with the BMW X5 Sport for the title of 'most compromised suspension'. The air suspension nicely irons out the smaller road imperfections that seem to completely faze the steel sprung set-up, while still giving the firm control needed during bigger suspension movements. Air suspension also includes adjustable dampers with three settings from 'comfort' through to 'sport' that improve things even further. You'd curse daily if you mistakenly opted to stay with the standard set-up.

The S has the same V8 4.5-litre engine but sans turbos, with an entirely reasonable 340bhp at its disposal, together with 310lb ft of torque. Although that's around 30 per cent down on the Turbo, the gearing's been lowered by around 10 per cent to compensate. Combined with a 110kg lighter kerb weight, this means the Cayenne S still feels reasonably brisk on the road, just lacking the turbo punch that its big brother possesses. To play catch-up you tend to make more use of the manual function of the Tiptronic gearshift on the 'S' - let the six-speed auto do its own thing and it hunts all over the place, a consequence of the Cayenne's scale- crushing weight and an engine tuned more for power than torque.

What really differentiates the Porsche Cayenne from other SUVs is the super-quick steering, just 2.65 turns lock-to-lock, giving this car fantastic agility for something so big and heavy. Combine that with specially developed tyres, simply massive anti-roll bars, a 38:62 front-to-rear power split and a body height some six inches lower than a Range Rover, and the 'S' does feel much easier to hustle than most of its rivals. That said, I'm not so sure that an X5 would disappear in the rear-view mirror quite as quickly as Porsche would like to make out.

This all sounds very promising from an evo perspective. But then, for some strange reason, Porsche has gone all-out to make the Cayenne perform exceptionally well off-road, even though hardly anyone will actually venture into the boonies in the boulder-bashing Porker. Of the maximum 10 per cent of owners likely to come over all Indiana Jones, less than half of them will really need to use all the 273mm ground clearance on offer. Yet huge efforts have gone into providing a central diff lock, low-ratio gearbox, a special traction control, together with excellent approach and departure angles. Frustratingly, all this leads to compromises in the chassis for the remaining 90 per cent of road-only users thanks to the inevitable higher centre of gravity; to make matters worse, this off-road focus hasn't helped the car's styling either.

This Cayenne is one of the most uncomfortable-looking cars out there. It seems so out of character for Porsche, renowned for its clean designs even when lending its name to chic coffee machines and sunglasses; think Porsche and elegant functionality springs to mind. But not with the Cayenne. Its functionality is bluff, fussy, oversized. That admittedly excellent off-road approach angle has led to the strange boat-like lines under the front bumper; the gaping front air intakes may do an excellent job of feeding the big engine with plenty of cooling when it's working hard at low speeds towing trailers up mountains, but they give the front end the appearance of a basking shark at feeding time.

The interior works much better. The dash, for example, is a superb piece of design, and the seating position is excellent. Yet it's not perfect for the driver; the narrow rear window, trio of rear headrests, and wide B, C and D pillars all gang up to give dreadful side and rear visibility. Initially, the clever opening window in the tailgate seems a nice alternative arrangement to the traditional clumsy one-piece rear door. But make sure you're over 5ft 8in tall before you use it - once open, the window ends up a ridiculous 7ft 4ins from the ground. This point isn't particularly evo, but it is particularly irritating. Ditto the 11.7mpg I averaged in the Cayenne S. Incidentally, the Turbo managed 10mpg over the same route.

I came away from the Cayenne S with mixed feelings. Yes, it drives better than rival SUVs but it never felt as sporting as I'd hoped. Frankly, I'd save up the extra for the Cayenne Turbo, as that really did seem special. And that's just how a real Porsche should feel: special.