Sean O'Grady has his preconceptions about SUVs confirmed by a particularly bad example of the genre

I've just finished driving the Mercedes-Benz M-Class ML350 and I'm pleased to say that I hated it. Pleased, that is, because it confirms most, if not all, of my prejudices about 4x4s. Thank you. Mercedes.

I've just finished driving the Mercedes-Benz M-Class ML350 and I'm pleased to say that I hated it. Pleased, that is, because it confirms most, if not all, of my prejudices about 4x4s. Thank you. Mercedes.

It is isn't very often that I feel so ill-disposed towards a car. I can't even really say that I hated the few cars that have managed to conk out during their time with me (Hyundai Elantra, Range Rover Vogue, Nissan Cube, to name and shame three miscreants). I was a bit annoyed that they'd let me down, but I didn't dislike them as such. But with the big 4x4 Mercedes I really didn't get on.

It was a "Special Edition" run-out model, with extra equipment and a £36,000 price tag, but that just made things worse. I felt bad driving it, because, unlike the Range Rover, say, there were no redeeming features such as the British car's beautiful interior and attractive lines. The M class had nothing to be said for it.

For a start, the Merc was a terrible car to drive. I don't know what it's like going through the Serengeti, but on the A43 it was no fun at all. It rolls around like an old dreadnought in a gale, but, I think, without a dreadnought's inherent sense of dignity.

The point about these luxury SUVs is that they are supposed to drive like proper cars on the road as well as being great for off-road work. That was the idea behind the original Range Rover way back in 1970, and, arguably, the rather less tastefully done Jeep Grand Wagoneer of 1963. Well, the Mercedes certainly didn't live up to that ideal, and there were times when it felt a little too wayward for my peace of mind.

The last time I drove something this roly-poly I was behind the wheel of a SsangYong Rexton. The Mercedes has a separate chassis, a very old-fashioned type of arrangement, which makes it hopeless at going round corners and far less crash-friendly than the latest designs, although it is also cheap to manufacture.

While SUVs may well be very good for their makers' profit margins they are not so good for you, the owner. If someone runs into you or if you are silly enough to hit another car, you'll most likely come off best, but they are much worse at avoiding hazards when you need to change direction in a hurry and their bodies may be less deformable in a serious impact.

You see, force equals mass times acceleration, and there is an awful lot of mass on an M class. So I am right to think them less safe, even for their own occupants, than an equivalent conventional car.

OK, so the M class is no Golf GTI - we knew that - but it is big isn't it? Well up to a point. It has the familiar SUV "reverse Tardis" effect; big on the outside, small on the inside. Indoors the M class doesn't feel that roomy and , if you fold down the two auxiliary seats in the back, the boot is almost tiny. It compares very badly with a Renault Grand Espace, which, at £34,000 for a well-equipped petrol V6 version, is about the same price as this Mercedes, will give you seven seats, more versatility and is a generally more classy environment to transport you and your family.

Which brings me to the M class's interior, which is nothing to write home about. The Special Edition version I was testing had plenty of kit but not all of it seemed to work.

Any sat-nav system that tells me that the A40 is off-road cannot be all there. The special edition model also lacked controls for the stereo on the steering wheel, pretty much standard fare on posh cars these days, and, more alarmingly, one of those bleeping systems to warn you that you're about to reverse into a bollard.

You get a lot more class in virtually any other Mercedes offering, including their much improved new baby, the A-Class, and virtually anything else on the market when you're paying the best part of £40,000. A Renault Espace is certainly a more civilised place to be.

Then there's the question of running costs. Here I have to concede some ground. True, the M class does much worse in CO2 emissions but finds itself in the same tax "bracket" as its French rival. Much more to my amazement, the M class actually returns much the same - appalling - fuel consumption as an equivalent Grand Espace (around 23mpg). What's even more, it retains £2,000 more of its value after three years' use. Given that depreciation is much the biggest cost in running a car like this, that is a significant factor, although it still it doesn't make up for having to drive a tank around.

A much more telling comparison is with the Mercedes E-Class estate. Yet here too I'm afraid I have had some of my prejudices challenged. For an E-Class estate is even longer than an M-Class SUV, although of course it is narrower, and thus much happier on a city street, until the time comes to park it. On the other hand, the M-Class, like other behemoths, won't fit easily into some multi-storey car parks, so some points are lost there. The two are about the same on boot space, though the E-Class holds a bit more of its value and is easier on fuel. So overall I still feel vindicated in my anti -SUV stance. The SUV loses out again on rational motoring grounds for most drivers - but not by as large a margin as I'd expected. But if I had £37,000 to spend I know where I'd put my money, and I know which car I'd rather be in in a crash. The E-Class represents all the old Mercedes virtues; properly built in Germany; about the last of the traditionally over-engineered vehicles; a life-saver in an accident. The M-Class represents all the new Mercedes vices; spreading the brand thinly, sacrificing quality for volumes, even making stuff in the US, for heaven's sake. Where will the madness end?

The good news is that the Mercedes M-Class dies soon, and is being replaced by a new M-Class which, they promise, will be much, much better and tempt some badge snobs out of their BMWs and Volvos. The amazing thing perhaps is that some 350,000 M-Classes have been bought since it came out in 1997. How many of them have ever ventured a wheel off-road? How many were used simply to take the kids to school? How many were bought simply because the M-Class has the biggest, most visible three pointed star you can buy without going to a Mercedes van or truck dealer?

You know the answers.

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