Swiss Alps: High Anxiety

I'm French-kissing a rock face and I don't want to stop. Because stopping would mean having to put my tongue back in my mouth. And if I do that I think I might never stop screaming. To be honest, I hadn't asked the rock how it felt about the situation. When you're 850 metres above ground clinging to a slippy, muddy and - most importantly - tiny metal rung sticking out of a cliff face, you tend to forget about etiquette.

I've been harnessed onto a wire threaded around what has been dubbed "Hammer Head Corner", a rock face devoid of natural ledges, steps or indeed any indication from nature that humans should trespass here. Thanks to this precaution, I know I won't die if I fall. But one wrong move and I will slip and slam into the slimy rock beneath me before having to inch up my safety rope, clamber back onto the greasy rung and, nerves suitably shot, continue on this three-hour assault against rational behaviour.

What is it about Switzerland? You're either eating fondue in its major cities or getting scared to death by its rural pursuits. Where do you find the comfortable middle-ground in this supposedly neutral country?

The via ferrata was not designed for extreme sports enthusiasts. The name means "iron road" in Italian, and the system was originally constructed in the Dolomites during the First World War: a vast networks of ladders and rope lines that that helped the embattled Italian and Austrian infantry in their efforts to regain control of the strategically important region. But now there are via ferrata routes built solely for "pleasure" all over Europe. They're considered a safe way for beginners to experience serious mountain climbing without any climbing experience (you simply buckle your two harness straps onto the rope line and start walking).

The important difference about the brand new route that is currently scaring the life out of me in Mürren, high in the Lauterbrunnen Valley in the Jungfrau region of Switzerland, is that this via ferrata goes downwards. It descends 300 vertical metres over 2.2km down an exposed cliff face. My calves, as well as my nerves, are feeling the strain.

Below me - far, far below me - sheep cling to the lower reaches of the mountain like pale cake crumbs. Barns with roofs the colour of smoked salmon are surrounded by fresh grass on the bottom of the Lauterbrunnen valley. Trees run like streaks of paint down the mountainside at impossible gradients. This is the kind of view of a village you normally would only get from "Google Earth". The inky black wall of the north face of the Eiger lies opposite me on the other side of the valley. It looks surprisingly welcoming compared with my present position.

My legs feel like coat-hanger wire wrapped in sponge as I gingerly stretch my quivering pins to get from one tiny rung to the next.

Several centuries later, I finally put my insanely unsuitable urban trainers onto what is, thankfully, something approaching solid earth. It's still slippy as hell and there's no room to turn around, but compared to clinging onto the metal rung on the rock face, this is like touching down onto the shagpile carpet of a luxury hotel. But the terror is due to continue. Next I must negotiate the "Flying Fox", a no-holds-barred version of the zip slide that you find in adventure playgrounds. This one zips across a gaping ravine. Oh, and there's no seat.

I crouch into a strange version of the foetal position and cling to the overhead wire as it carries me across the valley. "No Schnapps yet!" shouts the climber behind me (many people climb solo but guides are always available and you can't do the Flying Fox without one on hand). "Not until after the Nepal Bridge."

By the time I reach it, the bridge is swinging like a drunk pendulum. In fact, it's the sort of bridge that, were Spielberg directing my day, would be cut by machete-wielding marauding tribesmen. It's 80 metres long, there's a barely visible river at the bottom of the chasm it traverses, and it only becomes apparent when I begin to edge my way across that there isn't anything solid to cling onto, just another twirling rope. Yes, I'm harnessed, but I'm also experiencing real buttock-clenching, eye-watering, teeth-clattering, heart-stopping fear.

Why am I continuing to do this? I realise that it's nothing to do with heroism, overcoming my demons, or anything like that. I continue inching my way across the bridge for the most British reason of all, namely that I don't want to inconvenience the Swiss. There's a lot of people behind me wanting to cross and, incredibly, I conclude that it's preferable to slowly walk across a ridiculously precarious rope bridge with a 400-metre drop into a ravine rather than delay a lot of annoyingly robust, elderly Swiss climbers.

A monologue of expletives that would make Derek and Clive blush tumble out of my chapped lips as I cross, desperately trying not to look down and mentally picturing the wine and bratwurst that await me in the village of Gimmelwald on the other side.

"I was panicking pretty badly at one point, you can maybe guess where," grins Martin Schurmann, a squat, muscled local from the village of Mürren who built this via ferrata (the opening of which was the biggest event that anyone can remember happening in this soporific ski village for years). Sensing I had found the experience somewhat frightening, he was attempting to placate me with wine.

He tries to tell me how he managed to get the rungs into the wall on Hammer Head Corner but frankly, I didn't want to know. I was still shaking and whimpering slightly. I should probably have gone to apologise to the rock face for snogging it on our first date, but I'd lost my nerve. Eight hundred and fifty metres of air between me and the ground seem to be bringing out my shy side.

To find out more about the Mürren via ferrata contact the Mountain Guides Office on 00 41 33 821 61 00 or go to www.be-je.ch. A guide costs Sfr95 (£46) per person. This includes equipment rental. The writer stayed at the four-star Hotel Eiger in Mürren (00 41 33 856 54 54; www.hoteleiger.com). Prices from Sfr135 (£65) per person including breakfast, based on two people sharing a room.