Mercedes, of course, had already decided that the M-class should be an able hillock-hopper, but didn't go the full Land Rover. Hence a vehicle that's seriously compromised whichever angle you view it from. To make matters worse, build quality, normally the great justification for buying any Mercedes, was woeful (all early cars were made in the US, most petrol-engined models still are). Even with the attentions of AMG lavished on it, the M-class was a hard car to warm to.

With the X5 now clearly showing the path Mercedes ought to have taken with the M-class, a mid-life overhaul has taken place, involving some cosmetic titivation, build quality enhancements, suspension refinements and - best of all - a new 5-litre 288bhp V8 motor to replace the old 4.3-litre unit. There's also a new twin-turbo V8 diesel, stolen from the S-class, but right-hand-drive markets won't be getting it.

Mercedes says 1100 components have been changed but isn't able to say if that includes iddy-biddy bits like grommets. The new bits that interest us are front and rear bumper units, a wider grille with chrome decor on V8 models, projector headlamps, S-class-esque door mirrors with indicators inset, and larger wheels. Interior highlights include better quality plastics, a redesigned centre console with new switchgear, and the impression that the blokes who build these things now realise you should keep turning screws until components stop rattling.

What's new under the bonnet is the component that really counts for evo readers. The three-valve-per-cylinder V8 of the ML500 not only boasts power aplenty but a torque output of 325lb ft, served up on a plateau between 2700 and 4250rpm. The combo of that motor and a five-speed auto, using slightly shorter ratios than the outgoing 4.3, endows the ML500 with the ability to rumble from rest to 62mph in 7.7secs; not bad for something with the frontal aspect of a beach hut.

It sounds the biz, too, all muted muscle-car under full throttle, but with noise receding to limo levels when you reach cruising speed. In many ways the ML500 is a better car than AMG's overtly sporty ML55 (also revised though not in the engine bay), being almost as quick but seemingly performing with less effort and bluster. The AMG makes a meal of going fast, roaring and bellowing from up front, banging and crashing from below, all of which would be acceptable - enjoyable, even - if it created a significant advantage over its less powerful sibling. But it doesn't.

The ML500 is a more contented and comfortable animal. Its 'sportier' suspension settings don't quell the body lurch much, but there's a nicely progressive rate of roll and similarly well-controlled behaviour over lumps and bumps. The brakes also have a friendly, steady-rate action, so once you've got used to the bulk of the big Benz, you can soothe it down the road with a degree of decorum and at surprisingly high average speeds. Of course, your passengers won't thank you much, but if they can't take a joke they shouldn't have climbed aboard...

Still, you can always tell them they'd be worse off had you spent an extra ΂£10K and bought the ML55. It seems almost like heresy to be critical of the AMG with its hand-built motor, chunkier brakes, etc, but the ML500 proves that it's an M-class too far, and too costly.

If you must have a brisk M-class, the ML500 has much to offer over both previous-generation MLs and the brusque AMG. Its engine is rich in power, torque and character, its suspension provides good manners if not ultimate control, the whole thing's now properly built from superior materials, equipment levels are up, and should the urge to abandon the Queen's highway overtake you, the M-class is now more mobile in the mire.

It's still no X5, but then Mercedes sells as many M-classes as it can make, and with the latest improvements seems set to continue to do so.