This is Garburn Pass. The roughest, most extreme road still open and accessible to the great unwashed public in Great Britain. Harsh and inhospitable, it isn't for the faint hearted by foot, never mind by car. And we're about to try to drive up it in the new Land Rover Discovery 3. I don't know whether to laugh hysterically or weep gently into the sodden pages of my Last Will and Testament.

High above the cosy teashops and slate-grey hotels of Windermere, there lies a very different Lake District. If you're feeling adventurous, there are over 100 tracks that enable you to drive to remote, majestic views; but be warned - most are desperately rough, rugged and unkempt. And the Garburn Pass is the worst of them. The four-mile road that connects the two villages of Troutbeck and Kentmere isn't so much a track as a rock face, yet it's an unclassified country road with a public right of way, meaning it's open to anyone who's brave or stupid enough to have a go. I fall into the latter camp.

Despite most SUVs never setting a tyre on anything vaguely muddy, it's important that the Discovery 3 is seen as a serious off-roader, because it's a Land Rover and that's what Land Rovers do. So, if anything should be able to be driven along the wilds of Garburn, it should be the Disco. If it can't, then it'll make this new Land Rover just another SUV, an image-breaker for rufty-tufty Land Rover. It's got a lot to prove.

To get there, it's a 270-mile motorway and A-road hack from London, yet the Discovery, fitted with the same 2.7-litre TDV6 diesel engine found in the Jag S-Type, deals with the journey easily. With 190bhp, it's powerful enough - with plenty of torque for overtaking - the ride is comfy, and the handling taut and precise for a car this size.

After a five-hour, mind-numbingly boring hike up the M1 and M6, we turn onto the A590 that takes us onto Kendal and then Windermere. Only on these smaller roads does the car feel its size - at 4,835mm long and 2,009mm wide, it's not that much smaller than the Range Rover. Inside, the levels of comfort and build quality are comparable, although it feels slightly more utilitarian with chunkier switches and big, prominent buttons. It's similar on the outside, too, and with its slab sides and severe angles, it's also got shades of Hummer H1 in some of the body sections. See one by itself and it's obvious it's a Discovery with that roof-line kink, but line it up against its forebears and the car looks as different as the original Mini does from the current version. So the same, only different.

On the outskirts of Troutbridge, the village where the Garburn Pass starts, we're met by two engineers from the Discovery 3 project, Mark Parsons and David Armstrong, in a Range Rover that saw service on the G4 Challenge. They're here for two reasons: firstly, you should never off-road alone - just in case - and secondly, they genuinely know what to do in these situations as opposed to yours truly, who just hopes he does.