On the road, the GLS gets very close to Mercedes’s claims of an ‘S-Class of SUVs’. Refinement is excellent and performance is more than adequate, so overall it’s a very relaxing, comfortable place to while away the miles.

As standard the GLS comes with air suspension, but its real party trick comes with the Advanced E-Active Body Control suspension set-up. This employs two cameras that scan the road ahead to prime the suspension in order to cancel out any ruts and bumps.

Without this system, the GLS can occasionally thump into large bumps, the body rocking across cambers and undulations; it falls short of the X7 in terms of both comfort and control. With it, however, the ride quality and body control are just sublime.

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E-Active Body Control can make a difference in the corners, too. In its normal setting, it helps to fight against body roll, leaving a stable platform at all times. However, switch to ‘Curve’ mode and it can actively lean into the corners. It’s at its best on motorways and fast, flowing A-roads, where it gives the feeling of a high speed train. However, on very twisty sections the system struggles to keep up. Regardless, the GLS feels is stable, predictable, and offers up strong levels of grip. The steering is light and precise.

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2023 Mercedes

GLS

21,269 milesAutomaticPetrol4.0L

Cash £155,000

View GLS

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2023 Mercedes

GLS

27,159 milesAutomaticPetrol4.0L

Cash £141,445

View GLS

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2023 Mercedes

GLS

39,413 milesAutomaticDiesel2.9L

Cash £53,700

View GLS

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2023 Mercedes

GLS

20,152 milesAutomaticDiesel2.9L

Cash £68,833

View GLS

It’s quiet on the move, too. The most audible noise at speed comes from the tyres, but this isn’t a criticism: it’s just that everything else is so quiet. A fairly slippery shape (at least by SUV standards) means that wind noise is well suppressed, while the engine only really makes itself heard when you ask for hard acceleration.

One area where the GLS falls short of the X7, however, is manoeuvrability. The BMW is available with four wheel steering, which makes town driving remarkably easy for a car of this size. Without it, the GLS feels rather cumbersome by comparison.

Engines, 0-60 acceleration and top speed

From launch, the GLS UK range has only one standard engine option: the 400 d, powered by a 325bhp 3.0-litre V6 diesel. It copes easily with the near-2.5 tonne mass it needs to haul about thanks to a hefty 700Nm of torque delivered from as little as 1,200rpm. It allows the GLS to cover the 0-62mph sprint in 6.3 seconds and achieve a top speed of 148mph.

It’s also remarkably quiet on the move and, although not quite as hushed as in an S-Class saloon, emits only a distant rumble under hard acceleration. It’s mated to Mercedes’ nine-speed automatic transmission, which for the most part goes about its business unnoticed.

One car that certainly won't go unnoticed is the the Mercedes-AMG GLS 63 model, which takes performance on to supercar levels. Its 4.0-litre V8 petrol engine produces 603bhp and a colossal 850Nm of torque. 0-62mph is dispatched in 4.2 seconds, and the top-spec Night Edition Executive version will power on to 174mph.