The Mog is the Mercedes yearning for mud

The Mercedes-Benz Umimog U500, a "monstrous mountain goat", is hard to beat when it comes to tackling rough terrain.

The Mercedes-Benz Umimog U500. Car Enthusiast Editorial Agency

As a child, did you ever get told off for playing in the mud, coming home covered head to toe in the stuff? It's an essential part of growing up, along with tumbling over the handlebars and falling from the highest branch.

That little-boy mentality remains in every man, even when we reach an age more appropriate to have children of our own. So the fact I'm giddy with excitement at the prospect of playing with the latest Mercedes-Benz commercial vehicle should come as no surprise.

Arriving at the challenging off-road track deep within England's Millbrook vehicle testing ground, even youthful exuberance can't prepare me for my first sight - a bright orange Unimog U500.

This is a vehicle that can trace its history back 60 years, so the legend of the mighty 'Mog is actually twice my age. Nevertheless, on first sight I'm suddenly 12 again, images of me kneeling on the carpet dragging it around a make-believe landscape flashing before my eyes.

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It's a challenge just to haul my body into the cab, as the floor is level with my shoulders. Once atop the air-sprung driver's seat, the layout and number of controls ahead of me is an awe-inspiring sight, more in keeping with the USS Enterprise than a motor vehicle.

Which is why I'm so happy to shake hands with my Unimog expert, John. In truth, I'm too overwhelmed to pay him the attention required, his explanation of the levers and switches failing to stick in my head. Thankfully, the truck starts in a terribly conventional way, a twist of the key firing the 6.4L straight-six into life. The gear lever is a simple push/pull arrangement, though it offers purely digital feedback, and my boot keeps getting caught on the steering cowling whenever engaging the ever so sharp clutch.

And then there's the steering wheel. Yes it's mounted in front of me, but it's almost laughably proportioned. At nearly six feet tall, my reach isn't inconsiderable, but even my outstretched arms fail to comfortably find the farthest section of the rim.

Wheel finally in my grip, we're off - me, the 'Mog and John - in the wilds of Millbrook's course, a layout designed to challenge the most capable of civilian and military 4x4s. With water splashes, log rolls, impossibly steep inclines, sand pits and deep ruts, it's sure to put up a good fight, not least because it rained last night, so the ground is now looser than usual.

And then there's a massive bang, and I'm suddenly thrown into the air, the sprung seat following my every move. Sat almost directly over the front axle, every large movement underneath is translated into the cabin. The relatively short 3.35m wheelbase means the rear wheels are soon swallowed by the same crater that the fronts fell in and out of, and the rear of the 'Mog shoots upwards like a bucking bronco.

It's then that I'm aware of the lack of a front overhang in the U500 - most other vehicles would have ground their nose on entry, but not so the 'Mog. Where my feet lie, the front end pretty much finishes, which is a strange sensation. Of course, it's also the reason why the Unimog is so good off-road, the front end boasting a 28° approach, and the rear a 53° departure angle. A look through the specs also reveals a fording depth of 1.2m and a tipping angle of 38°, while slopes of 45° should prove no problem. And with tyre pressures that can be adjusted from the cab and a variety of differential locks to improve traction, it makes for reassuring reading - the U500's clearly made of some pretty tough stuff.

And so it would seem, despite the body movement over our first challenge, I'm being a little too gentle with John's 'Mog. When questioning his wisdom, my enquiry is met with "that was nothing, she can take much, much more" - clearly I'm too busy worrying about damage, barely scratching the surface of its abilities.

Challenge set, I tell myself to be more forceful come the next obstacle, which is all well and good, but when faced with the water splash, it's clear the combination of a scaled-down lake and the U500 will create more than a ripple. Still, that fording depth means its no problem for this man and his machine, and exiting the other side, both feet remaining dry, it's on to wilder and wackier obstacles.

Looking at an impossibly steep hill, John suggests giving it some gas as we hit the bottom of it, holding the engine in its sweet spot of around 2,500rpm. Duly obliging, I do my best to feather the throttle as we're thrown around, climbing the hill like some form of monstrous mountain goat. Despite the loose surface and deep ruts, we're soon at the summit - common sense suggesting we'd be unlikely to reach it in such a vast machine.

It's not only vast, it's heavy too, which is why I'm looking down from the summit wondering how to maintain a slow and steady descent to flatter ground. There's none of the electronic hill-descent control systems so often found on passenger cars, but there is simple engine braking and low ratio gears, so even the most cliff-like slopes pose no problem.

With common sense out the window (it really doesn't apply when behind the wheel of a 'Mog) we move on, and after slipping and sliding around the route, my 20 minutes are nearly over. Not before one last test though - a sideways slope, constructed of clay and featuring a rut clearly big enough to swallow a Land Rover Defender in one gulp.

Instead of skirting around it, once again I'm encouraged to tackle it head on, John ignoring my suggestion that the U500 could be lost to the English countryside forever. Nosing forward, the landscape turns on its side, and we're at an angle that could spell the end for all of us. The front right tyre dips into the crater, and the nose drops briefly as I consider closing my eyes. Then, what feels like an age, but is probably closer to three tenths of a second later, the landscape levels and the clay jaws are behind us and I'm ready to climb down from the saddle. The only fuss, drama or trepidation was in my head, the U500 simply shrugging it off, as if it were a hatchback used to pick up milk from the local shop.

Behind every bush, round every turn, over every hill, through every water splash and along every muddy rut, the Unimog simply dispenses with whatever is thrown at it. In any other 4x4 I'd be spending much of my time outside, getting my boots muddy checking the ground to see if my automotive companion could cope. But in the mighty 'Mog, I simply sit comfortably in the driver's seat and let it do its stuff. It proves to be far more capable than me, and despite the advancing years of the concept behind this 4x4 truck, it shows no sign of slowing down anytime soon.