EVEN an iconic image can't ward off the critics - and in the case of premium car maker Porsche the biggest target for ridicule has been the Cayenne 4x4.

Initially lambasted for its big, brutish shape, no sooner had the German manufacturer made the Cayenne look more appealing than a fresh assault was launched with the decision to introduce a diesel engine.

For chalk and cheese substitute Porsche and diesel was the general theme from the holier than though aficionados.

The figures, however, tell their own story, the oil-burning model accounting for some 57 per cent of all Cayenne sales and the range occupying second spot in the overall Porsche line-up behind the 911.

Power comes from a 3.0-litre V6 turbodiesel engine that delivers 240bhp of punch via an eight-speed Tiptronic S automatic transmission that includes gearshift controls on the steering wheel.

It's a refined and impressively quiet unit that can propel the big SUV from zero to 62mph in 7.8 seconds yet still return an average 38 miles per gallon, pretty impressive from an off-roader that performs and handles like a sports car.

In fact the acceleration time is identical to that of the 3.6-litre petrol-powered version.

The latest Cayenne is longer, lighter, closer to the road and more comfortable than before. It looks better inside too.

A 40mm longer wheelbase means extra interior space, so there's enough room to swing a cat, and the boot can cope with the kitchen sink and half the bathroom if you need to shift it.

And not only is the centre rear position comfortable - not always the case in so many categories of car - but the seat bench can move forwards or back by 160mm while the backrest has three position settings.

Design-wise the most striking feature of the cabin is a rising centre console that now surrounds the gearshift selector to give a more typical Porsche cockpit character.

On the negative side, the speedo readout is too small, as is the digital clock.

Standard spec on every Cayenne includes leather upholstery, dual-zone climate control, parking sensors, cruise control, sound system with seven-inch touchscreen and eight-way powered seat adjustment.

All models also come with Porsche Traction management all-wheel drive, though you have to pay an extra £2,330 for the likes of self-levelling air suspension.

In fact the tested model included no less than £13,000 worth of extras from cheaper items like a £317 heated windscreen - which made no difference to the condensation - to Porsche Communication Management with sat-nav at £2,092.

It isn't, however, the last word in luxury. For instance something you might expect to be included, like heated seats, is an extra cost option.

Porsche says that the Cayenne Diesel is proof that a 100-metre sprinter can also run a marathon.