I think it must be because the current Mercedes ML is such an old shed that this new one seems so good. From the moment the door clamps shut behind you and you drink in the conspicuous luxury of the cabin, it’s pretty evident that Mercedes is stopping at nothing to put to rest the reputation for shoddy quality earned of late by its car ranges in general and the ML in particular.

And when you fire up the new V6 diesel motor that powers the ML 320CDI (the car that will account for the vast majority of sales when it reaches British showrooms in September) and glide off ever so smoothly down the road, you’ll think you’re witnessing an off-roader revolution.

Within minutes it’s as clear as the three-pointed star on its bonnet that this ML is not merely improved, it has been transformed. So the only real issue remaining is whether this transformation is enough.

You see, a transformation would have been required just to bring the ML on to level terms with the likes of the BMW X5 and Volkswagen Touareg. But now we live in the age of the Land Rover Discovery 3 and the game has moved on again. Mercedes sidesteps this issue by saying the Discovery is a bigger car and that all bar the cheapest version have seven seats.

By contrast, while a sixth and seventh seat were options on the old ML, the new car is strictly for five only. Smaller it may be, but not cheaper. You can buy a seven-seat Discovery for £28,995 — £5,000 less than the cheapest ML, the 280CDI, is likely to cost.

The ML 320CDI will cost even more — probably about £37,000 — but is half a ton lighter than the Land Rover and, with its 224bhp engine, considerably more powerful than the 193bhp Discovery. Better still, the Mercedes engine, if not as eerily hushed as that used by Land Rover, is sufficiently refined to fool all bar the most sharp eared into believing it’s petrol, not diesel. It’s quick (0-62mph in 9.4sec), frugal (30.1mpg) and a model citizen in a community of generally still too noisy diesels.

Indeed the only flaw in the driveline is its gearbox. Not only can you no longer buy an ML with seven seats, you can’t have one with manual gears either. All are fitted with the world’s only seven-speed (count ’em) automatic box, which is nothing like as clever as Mercedes thinks.

Almost all its rivals use the same six-speed automatic built by ZF and which possesses an almost uncanny ability always to be in the right gear; by contrast the Mercedes box is less intuitive, has oddly spaced ratios, no sport mode unless you buy the special off-road package, and awkwardly positioned buttons behind the steering.

But if all you do is select D from the gear selector and cruise, the ML makes a strong case for itself. Ride and refinement are conspicuous strengths and if you choose the optional air springs (for an as yet unspecified four-figure sum) it will waft around with almost luxury car conviction. And, as Mercedes knows well, this is all most of its new owners will expect.

I was allowed to drive the ML off-road, but only in a car fitted with off-road tyres, the low-ratio box and hill descent control, none of which comes as standard.

Because of this it’s impossible to say how a standard car of the type that most customers will buy will fare when the going gets tough. The heavily modified ML was capable enough but as the course had been specially designed to showcase its talents, perhaps that’s no surprise.

I’d have been more impressed if they’d given me a standard car, shown me a peat bog and told me to get on with it.

Then again I doubt Mercedes will lose too many customers over the off-road issue. Indeed if you truly want to understand the new ML, it’s best not to think of it as an off-roader at all. Really it’s an alternative estate where your kids can sit up high and enjoy the view and you can look down on other road users.

Seen in this rather less demanding light, the ML is an altogether more convincing contender. The quality of its materials and construction is as good as any in the class, it’s spacious enough in the front, back and boot for a family of five and, with the diesel engine fitted, will cruise for hours in silence and comfort.

In short it’s good enough to propel the ML from just about the bottom of the class right into the thick of the action. If you really enjoy driving, a BMW X5 will probably be more to your taste, and if you need guaranteed off-road ability, seven seats or simply the best car in the class, the Discovery 3 will fit the bill.

But if all you want is a quiet, smart-looking, comfortable and capable family hold-all that will ask as little of you as you do of it, then the new ML pretty much fits the bill.

Vital statistics

Model Mercedes-Benz ML 320CDI
Engine type Six-cylinder, 2987cc
Power/Torque 224bhp @ 3800rpm / 376 lb ft @1600rpm
Transmission Seven-speed automatic, 4x4
Fuel/CO2 30.1mpg (combined cycle) / 275g/km
Performance 0-62mph: 9.4sec / Top speed: 130mph
Price £37,000 approx
Verdict Much improved, but the Discovery is altogether more convincing
Rating Three stars

The opposition

Model Land Rover Discovery 3 TDV6
For Astonishing ride, refinement, off-road ability and looks
Against Excessive weight harms performance and economy

Model BMW X5 3.0d
For The best-handling diesel SUV, with a strong image
Against Cramped interior, stiff ride; it's getting old