Mercedes GL450

Comfortable inside and imposing to look at, the GL-Class has the measure of its rivals when it comes to space. It's also a re-fined cruiser and not as ponderous around bends as you might think. The Merc is a truly capable machine - although navi-gating a narrow country lane or parking up in a cramped multi-storey will be a test of nerves.

Pitched at buyers who think regular 4x4s are a bit wimpy, the £55,000 GL450 is the largest and most luxurious mud-plugger Mercedes has ever built.

Inspired by the legendary G-Wagen, the newcomer is simply massive. But the imposing machine is not relying on size alone to attract customers, as it promises to offer luxury, practicality and real off-road ability, too.

Taking styling cues from the smaller M-Class, the GL is beefed up with boxy wheelarches and angular, squared-off lines. It's unlikely to win any beauty contests, but it certainly turns heads.

There's only one spec level to accompany each model, so standard kit is very generous, and includes folding leather seats, sat-nav and the firm's COMAND cabin control system. The dashboard and doors are beautifully trimmed and the driving environment is laid out in a logical and uncluttered way. Yet while the COMAND unit saves space, its num-erous settings can be confusing.

It's the room on offer that impresses the most, however. Unlike many SUVs that claim to provide adequate seating for seven, the GL is a genuine people carrier. Two adults can be comfortable in the rearmost chairs, which is no surprise really, given that the Merc is 20cm longer than a Chrysler Voyager MPV. Push a button to lower the back row into the boot floor, and you're greeted by a huge luggage compartment.

As with other premium 4x4s, the Merc combines a civilised on-road ride with genuine mud-plugging ability. Only when tackling tighter bends at speed does the GL really begin to pitch and roll. Otherwise, it delivers a refined ride that belies its weight and size.

Straight-line pace is superb as well, thanks to a new 4.6-litre petrol V8 that offers 340bhp and a sensational 460Nm of torque. The 0-60mph sprint is taken care of in 7.6 seconds, while a 146mph top speed is equally impressive. Smooth progress is aided by the seven-speed auto, but the 2,600kg machine won't win any medals for economy.

On our test route, the car gobbled its fuel, despite claimed returns of around 28mpg. Still, in rough terrain, there's an arsenal of electronic gadgetry to keep the 4x4 going. A low-ratio gearbox, hill descent control, adaptive damping and air-suspension - which can raise ground clearance to nearly 300mm - ensure the GL-Class is brilliant off-road. But it's the newcomer's presence on tarmac that is sure to appeal to most buyers. There's no doubt the GL-Class will find an audience among 4x4 fans, who are unlikely to be put off by its sheer size.