A modern sport-utility vehicle may be the only way to arrive at a Hollywood premiere; we travelled to Germany to find out if it can also cut the mustard when the going gets tough.

Full throttle,” cried the voice from the instructor in the passenger seat. I took a deep breath as I tried to get my brain to overrule what my heart told me, which was that it was crazy to drive straight at a mini-mountain made entirely from loose stones – I’d get stuck, or, worse, roll over sideways halfway up the steep slope. But I swallowed my fear, floored it, and barrelled towards the stone mountain.

I was in a quarry in Bavaria, in a car identical to my own ML 420 CDI, finding out for myself whether this sports-utility vehicle was a tough offroader as well as a slick city cruiser. Real off-roading requires four wheel drive for sure, but it also needs proper ground clearance, short overhangs, a locking differential and a set of low gears. Unlike some fashionable off-roaders, the ML has all of these, and I was about to find out what that meant.

Amazingly, the ML scrabbled its way up the hill like a crazed beetle, negotiated a 180-degree turn and, with a roar from the V8 engine, flew over the crest at the top. Steep slopes need huge amounts of torque to negotiate and the ML 420 has 700nm, more than almost any other car on the market.

The next challenge was a kind of rock course more suitable for potholers than cars, with sudden dips and mini-walls. Where the climb proved the ML’s prowess in traction engineering, this was aimed at showing off ground clearance, overhangs and chassis strength: the forces at work could easily expensively ground a car, or even buckle the chassis. The trick here was to take it slowly and steadily: at a couple of points the car was balanced on two wheels. It all worked out, and I and the ML emerged unscathed at the other end.

Then it was the biggest challenge: a descent down a 50 degree slope made of loose gravel, followed by a track through a muddy lake and climbing a Z-shaped path up the pebble mountain. I put the car in the lowest of the car’s fourteen gears (that’s more than any other car on the road) and touched the brake pedal just occasionally to accumulate enough stones under the tyres to slow our descent. At the bottom, I switched rapidly as instructed into high gears, tore through the lake without getting stuck, then slowed down in front of the final, greatest challenge, the stone mountain. Locking differential on, front and rear; air suspension raised to its maximum height; lowest gear set engaged. Three, two, one, GO! I tore up the path, yanked the car around the first corner and then felt petrified as I approached the second hairpin at high speed, with a 30-metre drop below and nothing to stop me if I got it wrong. “Don’t slow down!” yelled the instructor. Resisting the temptation to close my eyes, I kept the throttle floored, negotiated the second corner amid a wave of flying stones, approached the final crest and scrabbled over before coming to a halt. I felt as exhausted as if I’d run up the stone-mountain myself. “Well done,” said the instructor, although I’m not sure he was talking to me or to this remarkable car. Certainly, back home in my ML, the school run has never seemed the same since. – Darius Sanai

Mercedes ML 420 CDI; www.mercedes.com