Being built in Alabama, USA, suggests why.

Without a big SUV, no car-maker rates in that segment in the biggest car market in the world.

The seven-seat GL-Class design brief was that it should take the offroad ability of the 27year-old G-Wagen and marry to it the attributes of a large luxury SUV. Something more than the ML-Class. Much more.

The front-on view is imposing in a typical Mercedes-Benz style.

Side sheetmetal is pretty conservative but there's lots of it.

And from the back you really get a sense of how careful you'll need to be when parking it in any typical Irish multistorey.

The real wide-open spaces are inside. Especially if you flatten down the middle and rear seats.

There's a fully carpeted area that looks almost adequate for a queen-size double mattress, with no danger of even a six-foot-plus kicking the back door. If a couple get stuck between motels crossing Texas, there's no need to spend the night in neckcricking reclined front seats.

With seats up . . . and the two rear ones are electrically stowable . . . there's still substantial luggage capacity even with a full complement of passengers.

None of which is likely to apply to Irish owners. If you pay a hundred grand and more for a car here, you're not the kind who gets stuck between motels.

But the daytime accommodation in the GL is fivestar. Trim is classic luxury, at the most basic in a manmade 'leather' and moving up from there to nappa depending on spec. The dashboard is smooth and uncluttered, with standard M-B centre-stack controls and a dual-dial main-instruments cluster.

The review car is the 420 CDI.

It comes with burr walnut detailing, worth mentioning because it actually suits the car in its restrained application. The steering wheel has remote operation for both radio and phone. A cruise control/speed limiter is operated by its own column stalk. Being on the same side as the one which operates lights and wipers, it can take a little time not to flick inadvertently. But you do learn.

The car is powered by a 4.0 V8 diesel with 306hp and an astounding 700Nm of pulling power. With the seven-speed automatic gearbox, it is the kind of really smooth drivetrain that fits a top-end luxury car. You'll know it's a diesel but only because of the torque.

The autobox management is as simple as it gets: a small lever flickable between park, drive and reverse. For manual shifting there are a couple of buttons on the back of the steering wheel.

But why bother in a luxury cruiser where you've already paid handsomely for the car to do most of the thinking?

Don't wonder about the luxury features . . . the GL has them all, with only a few more as options.

Self-levelling air suspension is one standard, as is a trailertowing safety system that cools things if the tail threatens to wag the dog.

The drivetrain comes with electronically managed twospeed transfer box for those who go astray off the highway. This includes a second ABS system designed for offroad use. I didn't take the car offroad . . . in the Irish context the GL is not likely to be used even for pulling the horsebox for pony club outings.

But I've driven M-B's 4-Matic systems in difficult situations before and I've no reason to think the GL won't perform as required.

As a luxury SUV the GL-Class is as close as I've found to be a credible rival to the Range Rover . . . which started the whole thing off nearly 40 years ago.

VITAL STATISTICS

Model Mercedes-Benz GL 420 CDI 4.0 V8 TDI
Engine 302bhp
Length 5,088mm
Width 1,920mm
Height 1,840mm
Wheelbase 3,075mm
Acceleration 0-100km/h . . . 7.2secs
Top speed 230km/h
Transmission seven-speed automatic
Economy 9.2-15.6 l/100km
Price 119,850
C0 2emissions310g/km