The Mercedes-Benz GLS sits atop the firm’s range of SUVs as the most premium, most luxurious and most spacious of its off-roaders. It’s billed as the S-Class of SUVs, hoping to mirror the opulence of the firm’s most famous luxury saloon. Now, it’s been remodelled for 2020, with more technical additions and a sharper new look than before.

The GLS features an ultra-long wheelbase.

But can this leviathan of the road offer more than just outright size? We’ve got behind the wheel of it to find out.

Back in its third generation, the GLS arrives as an alternative to long-standing options like the Range Rover, or even newcomers like BMW’s X7. It’s longer than either of them – at 5.2 metres long – and at 2.2 metres wide, it’s one of the largest cars available on the UK’s roads today, in fact. But why this shocking size? Space, of course, and the ability to give all three rows of passengers a high level of leg and headroom.

The GLS corners remarkably flat.

There’s just one engine available – which we’ll get to shortly – while inside, it boasts all of Merc’s very latest equipment. A comprehensive adaptive air suspension setup has been included too, in the hope of making the GLS as comfortable and refined as possible.

As we’ve already mentioned there’s just one engine to choose from here, a 3.0-litre turbocharged diesel unit in the GLS400d. Sending drive to all four wheels via a nine-speed automatic gearbox, it produces 325bhp and a healthy 700Nm of torque. Mercedes claims that it’ll send the GLS from 0-60mph (0-97km/h) in a smidge over six seconds, while flat-out it’ll manage 148mph (238km/h). Economy-wise, we’re looking at up to 32.8mpg (depending on which wheel size you opt for), while emissions sit a 213g/km CO₂.

The GLS uses Mercedes’ 4Matic all-wheel-drive system.

It’s a brawny enough engine for the task in hand, that’s for sure, with that decent slug of torque meaning that the GLS should never feel out of puff. We expect a hybrid version to join the fray soon, but for now, it’s just this diesel – and that certainly seems like enough of an engine for most.

The first thing that strikes you when you set off in the GLS is the sheer size of the thing. It feels almost a postcode wide and just as long, which means it does take you some time to adjust. The ride also feels a touch on the firm side, despite the inclusion of Mercedes’ latest adaptive suspension system which uses sensors to actively adjust to the road surface. Of course, it’s not uncomfortable, but not quite as cosseting as you’d expect.

The front end design of the GLS is hard to miss.

But the engine is a real peach; refined and smooth, it suits the character of the car down the ground. The nine-speed automatic is also a standout feature, offering excellent responsiveness which leads you to wonder why so many others struggle in the same department.

Open roads are where the GLS feels at home, contrasting areas like the supermarket car park or on country roads where the car’s overall bulk feels like a definite disadvantage.

Despite being the size of Jupiter, the GLS doesn’t look overly large out on the road. Mercedes has done well to disguise its generous proportions with plenty of styling touches. The front grille ties the car to the rest of the firm’s range of SUVs, while around the back it looks like a slightly stretched version of the smaller GLE.

The GLS incorporates styling elements seen on other Mercedes models.

It’s a classy affair, mind you, and certainly reflects the car’s tip-top status in Merc’s range. Undercover shades like black and grey seem to suit it best, with lighter colours only helping to exaggerate the car’s size even more.

Those who have spent time in some of Mercedes’ smaller SUVs will feel at home in the cabin of the GLS. In fact, some may be disappointed that it plays so close to some of the firm’s other SUVs, given that this seven-seater is meant to be the crème de la crème. That said, it remains exceptionally well kitted-out, with good quality materials used throughout bolstering an already-heightened sense of solidity.

The interior of the GLS is beautifully finished.

There’s space in abundance – as you’d expect from a car of this size – and that’s the same for all three rows too. That’s the same for boot space too, with a very reasonable 470 litres available with all three rows in place, rising to a cavernous 2,400 litres with everything folded down. It’s easy to do that, too, thanks to buttons at the inside of the boot which carefully lower the seats.

The GLS is a car bristling with new tech. It features Mercedes’ latest MBUX operating system, relayed via a pair of 12.3-inch screens which sit together to form one seemingly seamless piece of glass. It incorporates a clever voice-operated system – activated by saying ‘Hey, Mercedes’ – which is one of the easiest and quickest of its type that we’ve experienced.

Stylish alloy wheels sit on all four corners of the GLS.

The operating system is sharp to respond and relatively easy to navigate. It might not be able to match BMW’s infotainment for out-and-out ease of use, but it’s still one which you can get up to speed within no time at all. The augmented satellite navigation is a particularly impressive function – it lays ‘directions’ out on the mapping, which ‘point’ you in the right way as you drive along.

The GLS is a true giant of the road, but it’s a fitting top-end to Merc’s range of SUVs. It might not have quite the truly rock-solid finish that you get in cars such as the BMW X7, but it’s certainly well-built enough to justify its price tag.

We do wish the cabin felt more elevated in terms of tech compared to other cars in the firm’s range, but for those wanting to transport six other people in sublime comfort, then you could do far worse than opt for the Mercedes GLS.