by Phil Vaughan

We've never had it so good when it comes to premium sports utility vehicles. And we've never had it so fast, either. The idea of a super-quick off-roader might be getting harder to reconcile against the current drive for a healthier climate, but there's no stopping the output of racers that can impress when rough-riding, too.

There is a bit of the Wild West mentality in all this - the guy who gets to be the fastest gunslinger in town soon meets his match.

As Porsche discovered once it had zoomed in front with the Cayenne Turbo.

With a 0-62mph in 5.6 seconds capability, and top speed of 165mph, you'd have thought that was performance enough for anyone.

It wasn't - not even for Porsche, which really pushed the 4x4 power boat out in early spring with the unveiling of a Cayenne Turbo S version.

Power was increased by improving turbocharger efficiency, with the eight-cylinder bi-turbo unit developing 521 bhp at 5,500rpm - 71bhp more than the Cayenne Turbo.

As a result performance leaps from very qiuick to neck-jerking. The Turbo S can hit 62mph in just 5.2 seconds, and has a top speed of 167mph, should you find an airfield or test track to prove a point.

Apparently this is not fast enough for its rivals, though with Chrysler, producing even more pace from the SRT-8 version of the Grand Cherokee.

The engine compartment of this beast houses a 6.1-litre V8 unit, producing a lesser output of 420bhp, yet it accelerates to 62mph in five seconds flat, with a top speed of 152mph.

As high-performance off-roaders go, the Cherokee SRT-8 is a bargain, too - £40,585, against the Cayenne Turbo S tag of £81,565.

Personally, if four-wheel drive acceleration matters, I'd have stuck with the Cayenne Turbo.

It is £70,870, and blends Porsche's sporting pedigree and reputation for build excellence very nicely with all-round ability and good practicality. Little details like the split rear tailgate help a lot.

It is a shame it doesn't share the attractive looks of the German roadsters - some would even denounce the Cayenne as plain ugly - but still has that instantly recognisable Porsche quality.

For a machine that is near-on five metres long and two wide, it has unbelievable balance and poise on the flat.

Flooring the pedal produces only minor kick as the suave six-speed tiptronic gearbox changes, racing up the rev counter. But is is the rapidly descending fuel gauge that might cause some concern.

The Turbo's thirst needs slaking at the rate of a gallon of unleaded every 18 miles, and if you fill-up from near-empty, make sure the bank overdraft is in place - the Cayenne's tank holds around 23 gallons.

Other costs to factor into running this off-roader include an insurance grouping of 20, a 35 per cent benefit-in-kind business user tax penalty, and the two-year - although it is unlimited mileage - warranty. With the power plant and chassis teeming with technology, repair bills could prove expensive, too.

It is rare that the Porsche will go off-road, but it is built to tackle tough territory, and has a ground clearance of around 11 inches - you can raise or lower the suspension to suit the terrain.

The Cayenne's black leather cabin was sparse but comfortable, yet supremely functional. Sports seats give excellent support, privacy glass (£229 extra) keeps rear passengers and cargo out of the limelight, and Porsche has added other extras such as a tyre pressure monitor (£404), an electric sunroof (£793), and telephone module (£523).

The total options added about £4,000 to the Cayenne Turbo's asking price, which is a lot to ask but afficionados with money to burn will doubtless be happy to dig a little deeper.

PORSCHE CAYENNE TURBO Top speed: 165 mph 0-62mph: 5.6 seconds Fuel consumption (combined) 18mpg.

Price: £70,870 Pros: Porsche technology Cons: Expensive options and fuel consumption Contact: www.porsche.co.uk