It all happens so quickly. One minute I'm happily leading the way down the glacier with my guide, Marty Beare, a few metres behind me, then suddenly the ground gives way and I find myself falling into a cre-vasse, my legs thrashing wildly beneath me.
Fresh snow has covered any tell-tale signs of the lurking chasm and I've broken through the thin crust. I've only fallen up to my waist, and thanks to Marty's quick reflexes, and the fact that we are roped together, I'm actually quite safe.
The instant he saw me stumble he braced himself, and because the rope has sufficient slack, something he had demonstrated earlier that day, he is able to arrest my fall and ensure I am held at the very edge of the crevasse.
Once I pull myself out, Marty has a confession for me: "I'm actually quite pleased you fell in, as it shows that what we teach in theory really works in practice."
Having scrambled and walked over many of the higher bits of the UK, I had long set my sights on bigger things, which is why I signed up for a week-long introductory course to alpine mountaineering. My base is the minuscule mountain village of Arolla, 2,000 metres up in the heart of the Swiss Alps. Arolla has a long history of alpinism, and Brits have spent more than 100 years clambering up the mountains that loom over it.
In the creaking, 150-year-old Hotel du Mont Collon, my home for the next week, they proudly display a letter sent in 1889 from a plucky Miss Richardson from Ripon, who describes her successful first ascent of the intimidating north face of the nearby 3,877m Pigne d'Arolla. No Gore-Tex, no GPS - what a gal.
Modern clothing is very much in evidence when our three-strong group steps out on to the nearby Glacier de Ferpècle for our first lesson: crampon and ice-axe technique. "It's essential you know the right way to use these, as all the major Alpine peaks are surrounded by glaciers," explains Paul Farmer, the head guide with Jagged Globe, the Sheffield-based company who run courses in the region.
Over the next three hours we practise marching up, down and sideways on the ice. A great number of mountaineering accidents happen when people trip on their crampons, explains Paul. The next subject we must tackle is a climber's most important piece of equipment: the rope. The classroom this time is the Aiguilles Rouges hut which sits above the Arolla valley.
As the mist scuds past the window, Marty demonstrates the classic technique of "taking coils", winding a rope over his shoulder half-a-dozen times before tying a knot and securing the whole thing to his harness with a karabiner.
The idea is that your climbing partner does exactly the same with the free end of the rope and you then move together, the standard mountaineering method for climbing over dodgy ridges and glaciers. If one of you slips, the other can stop the fall.
Our introductory training complete, we are ready to tackle our first Alpine peak, the 3,489m Pointe de Vouasson, beginning well before dawn the following morning. Summer ascents demand these yawningly early starts, as you need enough time to reach the summit and return to the hut before the strengthening sun begins to soften the snow and make conditions underfoot unstable.
It is a magical time to be so high in the mountains, and we pause to watch the sun emerge from behind the unmistakable silhouette of the Matterhorn. At the edge of the glacier, we rope up and fit crampons. The climb to the Pointe de Vouasson, a classic beginner's peak rated facile - the easiest grade - is straightforward, involving little more than a plod through knee-deep fresh snow and a simple scramble along the summit's ridge.
As we reach the top of our first Alpine peak we are rewarded with a handshake from Paul and Marty and the most dramatic view, of huge Alpine summits in every direction. The sun is shining in a seemingly cloudless sky when Marty points to a stream of wispy clouds to the south.
"Sorry," he says, "but those clouds mean a front is on its way."
By the next morning the front has arrived. This is the föhn, the weather system which can sweep across the Alps bringing with it notoriously stormy weather. Lashings of rain in the valleys, snow higher up and low cloud which races furiously across the peaks.
When the rain does subside, we walk to the Cabane des Dix hut where we are to spend the night before attempting our second and final challenge of the week, the Pigne d'Arolla. Built on an isolated cliff like some impregnable medieval castle and surrounded by a sea of glaciers, the Cabane des Dix is regarded as one of the best huts in Switzerland.
The evening before the climb the wind picks up, howling incessantly. Inside the hut, its roar is drowned out by the cheery banter of more than 50 climbers from all over Europe. But with little sign of the wind abating, it is likely to be touch and go as to whether we will be climbing the next day.
At 5am, we get our answer. Paul strides into our dorm and delivers a sharp bark of an order: "Get up!" Our route up the Pigne is likely to prove somewhat easier than that taken by Miss Richardson over 100 years ago, taking us up the glacier which streams down the north-west flank of the mountain from the summit.
Like our first climb it is rated facile, yet as we begin climbing we soon realise it is going to be far more difficult - and exciting. With chunks of ice the size of houses seemingly suspended in mid-fall above the glacier, and sheer cliffs rising into the cloud all around us, this is adrenalin-pumping mountain territory the like of which I have never experienced before.
To add to the drama, as we thread our way up the steepening glacier we teeter across snow bridges, sections of ice no more than half a metre wide which span monstrous crevasses. Then, just as we reach the top of the glacier and think all the hard work is behind us, we climb up on to the Arctic-like summit plateau and are hit by storm-force winds which send the temperature plummeting.
With my head firmly down, I doggedly follow Marty's footsteps in the billowing spindrift for what seems an eternity. Finally we reach the summit, and again receive a congratulatory handshake from Marty and Paul, but our view this time consists of little more than swirling whiteout.
When visibility improves on the descent I eventually see the tiny speck that is Arolla way down in the valley below, and in what seems next to no time we are sat in the village square, toasting our success with beers in hand.
So what I had I learned? That while it was easily one of the greatest adventures I've ever had, it was also one of the toughest, the most exhausting activity I've ever undertaken.
And while alpine mountaineering can at times be dangerous and scary, the good news is that all the safety procedures you're taught really do work. You can be taught to survive on a glacier, even if the bottom falls out of your world.
THE COMPACT GUIDE
HOW TO GET THERE:
Simon Birch travelled to Arolla by train. Fares from London to Paris on Eurostar start at £59 per person return; fares for onward travel to Sion in Switzerland start at £95 per person return. More information or for bookings: 0870 830 4862; raileurope.co.uk
A six-day alpine mountaineering course with Jagged Globe based in Arolla starts at £795. Details: 0845 345 8848; jagged-globe.co.uk