It's May 2007. A month is a long time to sit in a campsite watching the rain. A handful of trail runs, an aborted attempt on the Aiguille du Chardonnet's Migot Spur, and a couple of days' winter-style thrashing around in a blizzard somewhere on the Swiss side of the Mont Blanc massif are not amounting to the alpine season I had hoped for.

Bojan Uzicanin sorting his kit in the Midi station. The téléphérique is a gondola that rises 3000m up Aiguille du Midi. It is used by climbers, skiers and sightseers to get high faster.

Finally, a break in the weather sees Bojan Uzicanin and I throw a few essentials into tiny lightweight packs, bundle the rack into a plastic shopping bag (if it's good enough for Andy Kirkpatrick...) and jump on the téléphérique to the Aiguille du Midi top station at 3800m. Tonight's mission is the 600m Jager Couloir on the NE Face of Mont Blanc du Tacul.

We aim for a midnight start, but by 9pm boredom gets the better of us. After checking for signs of a refreeze, we kit up for the two hour walk to the base of the route. Stepping out through the tunnel onto the narrow arête always provides an unexpected dose of exposure, as a metre to the left the north face of the Aiguille du Midi drops away steeply to the Plan glacier 1200m below. Occasionally people self-arrest a slip on the initial 45-degree slope, but for those who fall it's usually a one-way ticket.

Half an hour passes as we make our way across the Col du Midi – the clear sky that greeted our departure from the station now less so – and before long, light snow begins to fall. Cold firm conditions underfoot encourage us to continue but it soon becomes obvious that something nasty is heading our way; the temperature starts to rise, the westerly picks up, and distant rumbles and flashes penetrate the cloud.

The Col du Midi is a large shallow bowl several hundred metres across. Hiding places from an approaching thunderstorm are scarce to nonexistent, as are alternative paths to ground for discharging lightning – especially when there are two guys standing in the middle of it waving metal sticks. Now I know what they say about crouching down on your pack, and all that good stuff designed to minimise exposure to a lightning strike. I also invite you to place yourselves in our position and try it some day, and see how you get on. As it is, we survey the rising storm, exchange glances, judge the distance back to the lift station.....and leg it.

The weather begins to deteriorate on the Col du Midi...

The cold firm snow is suddenly shin deep as we sprint across the plateau and begin toiling up the 200 vertical metres of ridge to the safety of the station. By now the thunder is deafening and each successive bolt of lightning leaves a searing after-image that dances across my vision. It is as though I am being pursued by the devil; or perhaps this is what it's like to flee gunfire in battle – not knowing, or having any control over, whether you will live or die.

Less than a hundred metres from the gate and we are onto the knife-edge section of the arête. A bitter metallic taste and a great flare of light as a charge explodes on the lightning conductor tower and crackling fire illuminates the doorway. Fifty metres, maybe less. Then BANG – or perhaps just the BA- of bang – and I am disoriented, legs up slope, on the end of the rope, poised for a headlong trip down to the Plan glacier. My axe is planted in the ground back up on the crest of the ridge. Bo is on his knees, clutching his head, the rope taut between us. He sees me and with eyes bulging screams 'RUN!!!!!!' at the top of his voice, as loud as I have ever heard anyone scream. Somehow I right myself and we scramble to our feet. Instinct takes over – that primeval, hard-wired, fight-or-flight state of being, which our bodies rarely invoke in our comfortable modern lives. Showers of sparks cascade off the cables above the doorway as we dive into the tunnel, chased several metres by tendrils of blinding white light.

Bo doubles over, dry-retching. For a while we just stand there, numb, adrenaline draining from our bodies, coming to terms with our sudden safety; with not having to run anymore. We look each other up and down, half expecting to see missing limbs, clothes burned away; anything tangible to justify our fear. Miraculously there is nothing – headaches and nausea last 24 hours but we have escaped injury. We can only assume that we have avoided a direct strike and were instead knocked over by the pressure wave of exploding air from a strike to the building. Either way we are lucky, and grateful, to be alive.

Suddenly safe: Bo in the Midi tunnel, after escaping the lightning.

Later we are told by station staff that they had known about the impending storm but forgotten to tell us. This does little to brighten our mood. They watched our battle up the arête play out from the comfort of their quarters, one tells us. They were waiting for us to be hit. Another returns with a couple of sleeping mats. We thank them and make our way to the toilets, the only warm place in the building. The smell is overwhelming but we don't care, though neither of us can sleep. We talk about waiting out the storm and heading back to the Jager in a few hours when conditions improve, but this is just bravado and neither of us quite believes it.

Dawn brings with it clear skies, the warmth of the sun and the greatest of all the mountaineer's resources – the selective memory. The ability to chalk things down to experience; never to believe that your number will be up on that day, despite the odds or what might have befallen those before you. Already the terror of only a few hours before has dulled; already we are planning our next climb; already we are buoyant and positive. Our love, enthusiasm and respect for the mountains is greater than ever.