A 10lb sledgehammer and a four-foot steel spike are this year’s must-have car fashion accessories . . . at least they are in Iceland. The lethal-looking tools are vital for smashing six-inch thick sheets of ice before fording frozen rivers. Sunglasses and T-shirts seem the order of the day in Britain now and winter driving accessories usually only extend to a bag of Werther ’s Originals and a Frank Sinatra CD.

But then conditions in Iceland are slightly more extreme, temperatures way below freezing, howling winds, snow drifts feet deep and tracks littered with tyre-shredding lava rocks. Here — as in many parts of Britain when winter bites — a 4 x 4, far from being an urban fashion icon and target of hate for environmentalists, is essential.

So where better to try out the Land Rover Discovery 3? With permanent four-wheel drive, the Discovery might be overengineered for the M1 but it is easy to spot in the company car park. How often, though, do British owners of this huge V6 diesel-engined machine need to use the Hill Descent button to crawl down ice-covered fields or switch to the grass/gravel/snow, sand, rock crawl, or mud and ruts settings?

How does the “Disco” go off-road, as in no road at all, not even a track, more a path, invisible under a foot and a half of snow, ice and rubble? Route One out of Reykjavik, heading south and east towards the Myrdalsjokull glacier, is one of Iceland’s main routes but even here, with good tarmac, the permanent four-wheel drive proves its value as the snow drifts like white smoke across the road and ice encrusts every side-road, pavement and forecourt.

Soon we turn off Route One — and into a white-out. The track is buried under snow and almost instantly a 30-foot long drift, up to three-feet deep, blocks the way. Behind us, a Toyota saloon sees the drift, gives up, does a quick three-point turn and disappears. I push a button, which raises the car’s suspension to increase ground clearance, then turn the dial to put the car into grass/gravel/snow mode.

Floor the accelerator and head for the drift and ten bucking, sliding, wheel-spinning, adrenalin pumping seconds later we are through the drift and ready to motor on.

A few miles on and a delivery van is buried up to its axles in snow. If you break down here you don’t need the AA, you need Ray Mears, television’s survival expert. We hitch the winch-mounted rope to the van and slowly reverse, dragging the van out of its snowy hole. Boy Scout job for the day done, we motor on.

Two hours later, we have covered just two miles, having repeatedly had to tow, winch and dig other Discoverys in our small convoy out of the snow. The moment you stop, your car appears to be sinking, when in fact the snow is building up around the car. The weather is so extreme we have to turn back and head cross-country using the dashboard mounted Garmin in-car navigation systems, favoured by oceangoing sailors, which has an ingenious “bread crumb” feature, which helps you to retrace your tracks.

The next day, Iceland’s dazzlingly changing weather finds us on the barren interior, used by astronauts to practise their moon-walk techniques. This time we are heading for the Langjokull glacier but a river blocks our way. Some 30 metres wide, it is frozen solid, which is where the sledgehammers and steel shanks come in.

After two hours of ice shattering, I climb back, sopping wet, into the Discovery and edge the car into the water. It is about two-feet deep and we crawl forward, pushing small icebergs to left and right with a sub-zero bow-wave forming in front of the car’s bonnet. Then comes the hard bit — getting out. Again, floor the accelerator and the car starts to climb out of the river on to the icy bank. It is like sitting inside a freezing washing machine as water and ice shards fly. Then the traction control gets a grip and we almost vault out and back on to dry land.

The next challenge is a series of ice and snow-covered hills and here the Hill Descent feature, operated at the push of a yellow button, does the trick, ensuring that grip is kept and the anti-lock brakes are intermittently applied without loss of control.

This was extreme driving, nothing like the school run or the trip to the supermarket — the simple tasks that offroaders are asked to perform daily. That is why many will never be won over by the idea of driving a 4 x 4. Then, only about 7 per cent of the cars on our roads are offroaders and, with a winter predicted to be one of the harshest on record fast approaching, the allure of a Land Rover suddenly makes sense. I know: I was that man with the sledgehammer.

VITAL STATISTICS

Model: Land Rover Discovery 3 TDV6 HSE
Power: 2.7-litre V6 turbo-diesel, producing 193bhp, driving all four wheels permanently
Performance: Nought to 60mph in 12sec; top speed 109mph, but it’s the grunt getting out of the snow that counts
Economy: 21mpg combined
Price: £43,495