The story of the Mercedes-Benz GL is, inevitably, about size. This thing is so massively proportioned that even American observers have called it crass. The Los Angeles Times described it as a vehicle for “selfish rotters” and “morally retrograde”. If it gets that reaction in the land of the Big 4x4, what sort of welcome can it expect over here? To put the GL in perspective, consider that other Merc off-roader, the not-inconsiderable M-class. Well, the GL is 308mm longer, 25mm taller and 300kg heavier. Over here, it’ll make the Range Rover look diminutive by comparison.

Blame America. Everyone else does, after all. The GL was designed as an upmarket alternative to behemoths like the Lincoln Navigator and Cadillac Escalade. Mercedes knows this and that’s why it is noncommital about how many will be sold in the UK.

All that said, for a beast that weighs nearly 2½ tons, the GL acquits itself remarkably well. The speed-sensitive steering responds swiftly to inputs, and its precision makes it easy to fix a cornering line. That such a monster can be driven so swiftly won’t, though, endear it to other road users cowering in its shadow.

Airmatic suspension is standard on UK GLs, as is the Adaptive Damper System (ADS). In Sport mode the ADS helps tie down the GL’s body control through dips and surprise off-camber moments, but the ride predictably suffers. In Comfort mode the ride is really very good, but you do trade off a bit of body control.

For off-road going, Mercedes wanted to give the GL credentials to stand comparison with a Range Rover. So with permanent four-wheel drive there is a low-range two-speed transfer case with multiple-disc limited-slip differential, which can be locked for really serious going. And to match Land Rover’s Hill Descent Control the GL features Downhill Speed Regulation, which trumps Land Rover by letting the driver set the maximum descent speed. So like the Range Rover, the GL has vastly more off-road capability than 99.99% of owners are ever likely to need.

Climb aboard and you’d be forgiven for expecting stadium-class accommodation. In fact this massive Merc is something of a reverse-Tardis. Three six-footers sitting behind each other in the GL’s three rows will find legroom tight. Simply put, this car isn’t as spacious as it looks from the outside. That optional third row of seats folds away electrically at the touch of a button, which is kind of neat. If you need more carrying space, the middle row of split-fold seats can be stowed by moving the seat squabs forward and dropping the backrests.

It’s a quick old truck, too. I drove the 340bhp 4.6 litre V8 (yet to be confirmed for the UK), which does the 0-62mph sprint in 7.6sec with a top speed of 146mph. The 7G-Tronic gearbox is a good match for this lively engine, too, as it is less prone to hunting for the right gear as it does on smaller-engined M-class models. It also has a manual sequential shift feature via rocker switches on the back of the steering wheel. When you’re pressing on a bit this can be quite handy. You almost forget you’re driving an apartment block.

There will be three engines available including the latest version of the excellent 320 CDI, which will probably be the pick of the range. Merc’s first V8 diesel for the UK, the 420 CDI, and a 388bhp 5.5 litre petrol V8 will also be on offer.

The GL models will be priced from about £50,000-£60,000. Mercedes says that there will be a universally high specification, so no different trim levels will be introduced.

Honestly, though, this has got to be the most pointless Mercedes launched here in memory. The only possible reason to buy the GL over the M-class is because you really need the optional extra two seats. And even then I’d urge buyers to look at the long-wheelbase Merc R-class, which has six seats and much more interior space.

This time, and for all the wrong reasons, size really does matter.

Vital statistics

Model Mercedes-Benz GL
Engine type 4663cc, eight cylinders
Power/torque 340bhp @ 6000rpm / 339 lb ft @ 2700-5000rpm
Transmission Seven-speed automatic
Fuel/CO2 21.2mpg / 322g/km
Performance 0-62mph: 7.6sec / Top speed: 146mph
Price £50,000-£60,000
Verdict An unnecessary addition to the Mercedes range
Rating 2/5
Date of release September 1

The opposition

Model Range Rover 4.4 V8 SE £51,045
For Great style, image, unrivalled off road
Against Quality still an issue, only seats five

Model Land Rover Discovery V8 HSE £48,540
For Spacious seven-seater, very good to drive
Against Quite heavy and consequently very thirsty