The GLS appears in just the one body style; unlike its GLC and GLE stablemates, there’s no option of a fastback-like ‘Coupe’ option here. Buyers can choose between six or seven-seat layouts, with the former offering individual seats for a VIP shuttle feel.

As you’d expect, the high ride height gives a commanding view of the road ahead, although it’s not quite as high as the G-Class’. For such a large car, the large glass area all round makes visibility fairly good, and for the areas which can’t be seen easily, a 360-degree camera is standard.

The GLS is a class leader when it comes to space. All three rows of seats can easily fit tall adults, while there are generous door bins and plenty of other storage areas dotted around the cabin.

Size

The previous GLS was hardly a compact car and the current version expands to even greater dimensions. At 5,213mm long, it stretches 83mm further than the old GLS, and 62mm more than the BMW X7, too. Including the door mirrors, the GLS is 2,157mm wide (it’s 2,030mm wide to the edge of the wheels – 30mm more than the X7) and it’s 1,823mm tall. The wheelbase measures 3,135mm.

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2021 Mercedes

GLS

51,269 milesAutomaticDiesel2.9L

Cash £52,850

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2021 Mercedes

GLS

69,339 milesAutomaticDiesel2.9L

Cash £49,990

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2019 Mercedes

GLS

56,000 milesAutomaticPetrol5.5L

Cash £39,995

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2021 Mercedes

GLS

66,000 milesAutomaticDiesel2.9L

Cash £49,950

View GLS

For those who plan to tackle fords and river crossings in the GLS, wading is possible in up to 500mm of water. Impressive, but less than the Range Rover’s 900mm figure.

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Leg room, head room & passenger space

If passenger space is the number one priority, then look no further than the GLS. Many cars offer space for seven, but in reality the rear seats are only good for children. Not so the GLS: in the third row, Mercedes claims that anyone up to six feet four inches tall will fit just fine. Those seats are heated, too, and each have access to their own USB charging points. They may seem a long way behind the driver, but thanks to a microphone system, it’s still easy enough to hold a conversation without raised voices.

Buyers can have the GLS with either six or seven seats. That means a 2-2-2 configuration which includes individual captain’s chairs for the middle row, while the 2-3-2 configuration uses a more conventional middle bench.

The three-seat option feels like it loses little in plushness though, particularly if the optional Rear Comfort Package Plus is equipped: this allows the centre seat to fold down into a wide armrest, featuring a removable tablet for controlling the comfort and entertainment functions. The middle seats can slide and recline and, like those in the back, offer acres of head and leg room.

The GLS is the perfect place to carry kids, and plenty of them: four ISOfix locations mean that there’s plenty of choice when it comes to child seats.

Boot

The vast exterior dimensions translate to not just impressive passenger space, but plenty of load-carrying ability too. Even with all seven seats in place, the GLS boasts a 470-litre boot; 80 litres more than the old car, 144 litres more than the BMW X7 manages, and comfortably bigger than the average family hatchback. Drop the third row and volume grows to 890 litres, while in two seat mode there’s 2,400 litres on offer. Each of the five rear seats can be lowered at the flick of a switch, and save for a slight angle on the middle row, lie completely flat.

The huge rear door makes access easy too, and the air suspension can be dropped slightly at the rear so it’s a little easier to load heavy objects. A parcel shelf can be fitted behind the third row to hide away certain items and when it’s not in use there’s space to store it beneath the boot floor.

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Towing

You’d expect the GLS, complete with a torquey diesel engine, advanced air suspension and a long, stable wheelbase, to be an excellent tow car – and you’d be right. Rated to tow a braked trailer weighing up to 3.5 tonnes, the GLS also features a system called Trailer Assist. All the driver needs to do is select an area on the touchscreen in which to position the trailer, and the system instructs the required steering inputs to achieve them. In our experience – with a driver who had never towed a trailer previously – it was very intuitive to use.