Mercedes-Benz M-Class

When Mercedes-Benz was demonstrating the new M to journalists, the company pulled the same trick that Jeep always does. You drive one car on the road, then do an off-road section in a different vehicle. And the two have different tyres. That matters: tarmac tyres can't get much of a purchase on mud, but mud tyres on the road feel like the steering rack's made of chewing gum. So the only test of a 4x4's breadth of ability is to do all terrains on one tyre. That's what Land Rover does, incidentally.

So I can report that equipped for off-roading the M-Class can get a long way off-piste, and that with its running shoes on it's well up to class best on the road. But only a side-by-side, like-for-like test with a Discovery will prove whether one single Mercedes set-up can do it all. I have to doubt it. It's not just tyres that were swapped; we also had a different mechanical spec on the muck section, the 'Off-Road Pro' pack. It gives you diff-locks, a two-speed transfer 'box for tricky crawls, a high-lift suspension and an underbody guard plate (to be fair, none of that should harm things on the road). To specify it, you have to buy the air-suspension (around $3,000) and then spend another wodge on the Pro pack. No-one will, of course, but if you can afford to fork out the extra cash, the M is seriously impressive off-road, although you do have to be handy with the various buttons that control all the hardware.

Is this relevant? Without the Pro pack, the M will still be perfectly capable of tackling an icy mountain road, towing a boat or negotiating a mucky track. Ground clearance is good, the traction systems work well and the seven-speed auto 'box has a pretty low first. And the body and suspension are just as strong as in the Pro edition, so it ought to be a lot tougher than most crossovers.

The new M has ditched the truck-like chassis of the MkI for a car-like monocoque, which is good for everyone's safety - those in the crashing M, and those in whatever it crashes into. It also makes it lighter and more car-like to drive. As car-like as any big SUV, really.

As we reported on the ML500 last month, it's not as sharp to steer as an X5, but the ride is hugely more acceptable. I say car-like, but you have to remember that's car-like in the context of off-roaders. An E-Class wagon still rides better and corners far more sharply. Same with the performance: kitted out with the brilliant new diesel V6, the ML320CDi is very torquey, smooth and economical for an SUV. But you keep thinking how great that engine would be fitted in a proper car.

No such ifs and buts about the cabin. It's just like a Mercedes car in here, and equipped as standard with a substantially more high-rise vista out through the windows. No worries about the quality either; Merc is trying extra hard with this one after the cruddy plastics and reliability of the first generation. And there's plenty of room for five adults - a longer seven-seater will be along in a year's time.

A similar, if lighter and more agile, 4WD chassis will be also sold next year as the six-seat R-Class, which looks like a photocopy blow-up of the B-Class. Then there's the truly hardcore gen-2 G-Class. They spoil us for choice.

Paul Horrell