In the hotly contested family-car sector, the Zetros suffers by comparison to its key rivals. The Insignia Tourer, for one, is far easier to reverse-park, while the Zetros’s 7.2-litre diesel engine simply can’t match the Mondeo Econetic for fuel efficiency. Its £80,000 price tag does make it tricky to justify beside the £13k Skoda Octavia, too.

It has the edge on legroom, mind. Mercedes guys call the Zetros ‘Unimog’s big brother’, and the Unimog makes anything smaller than a Challenger tank look a bit piddling.

Even this four-wheeler - there’s a triple-axle version available - measures eight metres from nose to tail and stands three metres tall. With the monstrous crane-device fitted to the Zetros we’re driving (we’re told it’s used for positioning telegraph poles, but suspect its true purpose may be rather darker), it weighs over 10 tonnes.

Getting into the Zetros’s high, high cabin is an athletic process involving the graceful ascent of a row of metal steps and the loss of all the skin from your left shin. Once you’re strapped onto the bouncy hydraulic driver’s seat, the cabin is surprisingly conventional with the exception of the 9spd manual. This has a conventional H-pattern (well, an H-H-H pattern, at least) and requires the dexterity of a brain surgeon to slot into third gear without accidentally selecting first, fifth or DESTROY ALL HUMANS.

On tarmac, progress is unexpectedly sprightly - nearly a thousand torques from just 1,200rpm will do that - but it’s the Zetros’s off-road ability that gives it the edge over even the Audi A4 Allroad. Cliff face, volcano, police blockade: doesn’t matter what you put before the Zetros, it shall be destroyed. Locking differentials, absurd axle articulation and an exhaust brake that sounds like a wheezy giant combine to give the Zetros such freakish, go-anywhere ability that it makes, say, a Defender look like a mud-fearing ballerina.

And so it should: this thing is designed to tackle warzones. The Zetros is Merc’s response to military forces’ need for an all-terrain truck able to drive straight into a Hercules plane: the Unimog, with its flat front end, kept headbutting the undercarriage on the way in. But though many Zetroses are destined for military use, they’re also employed by the emergency services, construction industry and Bond villains. Last year, Merc built a Zetros ‘camper van’ for a Russian who enjoys hunting in deepest Siberia. Who he hunts, we’re not brave enough to ask.

But the Zetros isn’t only for gun-toting Siberian oligarchs. If you’re a normal, caring parent with an HGV licence and a morning school run incorporating molten lava lakes and enemy checkpoints, this could be the perfect family car for you. Really, can you put a price on the safety of the little ones?

Sam Philip

The numbers

7200cc, 6cyl, AWD, 240bhp, 959lb ft, tiny mpg, silly g/km CO2, 0-62 in never, 55mph, 10,000kg

The cost

from £80,000

The verdict

ZETROS FEARLESS. ZETROS DEVOUR VOLCANO AND GLACIER AND DESERT AND HUMAN FLESH. ZETROS WILL OVERCOME! FEAR ZETROS!