Survival of the warmest in Telemark country

Icicles hang from our noses; our feet are glacial and our bodies tremble with cold, it's -20C outside and falling. Or I should say inside, because it is the same temperature inside as out. It's about 10pm and we're in a lavvu, a Norwegian tepee, high in the mountains near Evje in southern Norway, trying to keep warm inside our sleeping bags. The tent lining is so iced up that it looks like the midnight sky itself, the icy crystals shining like stars.

One by one we give up this sleeping business. There's only one choice: light the fire again, even though we put it out because the smoke from the damp logs hurt our eyes so much we couldn't see. Sitting now, rather than lying, in our sleeping bags, we cuddle up to each other around the fire, eyes closed tight. Andrew, the policeman from Spalding who never drinks, and Michaela, the biker from Brighton, get out the aquavit as Hugo, my husband, defrosts his jokes. It's 4am and we know we're not going to sleep – ever, it seems. "Help Me Make it Through the Night" won't stop going around my head.

Three of our group, who were trying to sleep in the snow-pits they made outside, have also returned to the lavvu, seeking warmth. They get laughter instead as the aquavit goes round. Being outside, though, is sensational: the heavens are blacky blue with white stars you want to touch and a gibbous moon so orange you want to eat it.

Brian Desmond, our guide and instructor in this icy madness, is the only one to have slept. "OK, I'm bringing forward the plan. Let's cook the porridge at six o'clock, pack up and leave at eight to ski back." The relief is tangible; that means only a couple of hours left to sunrise and the thought of porridge never tasted so good.

Brian may look a little like John Cleese but his manner is more 007; he's a master commando of winter warfare, having done 72 expeditions in far worse conditions than this during his 25 years with the British military. He's lived in Norway for more than 20 years, and teaches the British, Norwegian and Dutch military not only to ski but also snow survival. That's why he doesn't fool with the mountains, particularly when he has novices like us on our first "mini-expedition".

Brian's timing is perfect; having eaten the porridge – with the spoons we carved ourselves because we have forgotten to bring utensils – we get ready for the ski back to civilisation. Just as we finish clearing up, the day breaks. The deep cold has turned every living shape into a sparkling silhouette; hoarfrost coats every tree and plant with glittering silver fairy lights.

It is the most appropriate finale to one of the toughest nights any of us have ever experienced. A fitting end to the most glorious week being taught Nordic cross-country skiing; learning how to claw uphill in herringbone fashion (better with skins on your skis), glide downhill and run on the flat. As we skied, Brian taught us his skills: how to build snow-holes for shelter, bore ice-holes for fishing, cook sausages on sticks and shoot biathlon style.

We are an odder bunch than Brian usually takes on his skiing courses. For the first time he has teenagers – our children, Magnus and Lydia, and George, with his father, Carl, the Cheshire GP. There are also more women – the French lady, Caroline, as well as Michaela and myself.

Half of the group have never skied before, while some, like us, are down-hillers. There were a few agonising days for some, but despite bumps and bruises, everyone fell for the sport. Once you understand how it's all about gliding and skating, it is liberating and graceful. It's good for you, too; the number of octogenarian Norwegians flying past us was astonishing.

But the skiing is not the sole reason for being here. Most of us were inspired by The Real Heroes of Telemark documentary made by Ray Mears, the TV presenter and explorer, who organises this course. Mears had first sought out Brian's winter expertise to make the film. Brian also helped to track down the original Telemark resistance fighters for the documentary, which tells the story of their extraordinary journey across treacherous terrain to blow up the German heavy water plant at Rjukan (an epic tale made famous by the 1965 feature film starring Kirk Douglas and Richard Harris).

In many ways, our adventure pays homage to their daring; we even stayed in the former Norwegian military camp which the Germans took over in 1940, and which is occupied now by Brian for his courses.

As Michaela says when we leave: "Now I've seen this beautiful country, I can understand why those men were so brave to defend it. And, when you see them still skiing in their 80s, you know they'd do it all over again."

Compact Facts: How to get there

Introduction to Nordic Skiing is organised by Ray Mears at Woodlore, the School of Wilderness Bushcraft (01580 819668; raymears.com ) from £1,200 per person inclusive. Brian Desmond runs the Joint Services Training Centre, Evjemoen (destination.setesdalnett.com ) in southern Norway offering winter and summer activities such as canoeing and rafting.

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