Experienced skiers and ski writers know the risks. But like climbing into your car every morning, you expect to reach your destination safely without smashing into another vehicle. Drivers reckon it is a calculated adventure, even if the statistics of road deaths and serious accidents are pretty horrific. Like car crashes, avalanches are incidents that happen to others, including Royals. They can happen on-piste and off, even if they are invariably associated with off-piste challenge.

On a bright January morning at La Plagne in the French Alps, the Bellecote glacier and the runs flowing from it looked as inviting as ever. But the long off-piste run down to Champagny was the route for our small group of four, led by a ski school mountain guide and including Arnie Wilson, the Financial Times ski writer who lost his partner, Lucy Dicker, in a tragic ski accident two years ago.

I had just read his book about his round-the-world ski tour with his partner, appropriately called Tears in the Snow. After completing the record-breaking trip, skiing for 365 days of the year, Lucy died on a steep icy couloir - a gully - at La Grave in the southern French Alps. A mountain guide had led the party.

Such thoughts were never far removed at one level and well removed at another as Serge, our guide, slid under the piste marker rope at the top of the glacier and traversed over towards a slope you would only ski with a guide you trusted. There is general acceptance that if a man of the mountains says it’s OK, it’s OK.

The edges of the skis bit into the snow in the couloir. This was not the place to fall and every turn had to be executed perfectly. There is nothing like a steep slope to ensure your technique is trusty. I looked back up, impressed with my achievement. “I really quite enjoyed that,” I told my fellow skiers.

Out of the couloir, the snow conditions changed. “Wind,” said the guide. The dreaded, wind-blown crusted top, sat on a bed of heavy, sludgy snow. Sunshine and perfect views of the mountains of Vanoise national park could not hide the difficult conditions. Our guide stumbled a few times, even if he, and Arnie, could snake out turns in the vacant snow fields.

Serge searched for the best routes down, testing one direction, then another. In the expanse of the snow fields, it is not always apparent what is risky and what is not. I followed behind Serge, struggling to jump a turn at the top of a short slope that held its daunting prospects. Stemming a turn or two, I puffed more easily as I stood at the bottom of the slope, waiting for Miriam to follow.

The crack happened suddenly, a quiet rumble from the top, leaving a wide fissure of snow exposed to the sun. Cries of “avalanche” could not prevent Miriam riding the danger as the slope slid away beneath her skis. She tried turning and skiing out but it held her firm as she surfed the dreaded skiers’ nightmare. Something like 20m by 15m of slope had given way when it had not snowed for some days.

The slab avalanche had caught us. It did not take us under - there was not enough snow - but it pulled Miriam down on top of me. You would like to think you do not panic in such situations. But I couldn’t tell you.

The unexpectedness of the event and the sudden descent of the packed snow ensured I could not escape. I saw Serge ski out of danger. I was snared by my left leg and ski, trapped up to my groin in a sludge that felt heavier than anything I could have imagined. I was later told avalanched snow is heavier than wet concrete. It felt like that. Was my thigh broken?

Miriam, white as the snow she was struggling to break free from, was a couple of feet above me, her weight on the snow preventing my escape. The pressure was intense. Lying on her side and back, she kicked out her skis, and took a route over my left thigh. “Careful, ‘attention’,” I shouted, but I don’t think she heard.

Survival and escape are natural instincts. Once the weight was released, I, too, fell sideways and kicked out, relieved I was not a news headline after my first avalanche. Goodness knows what Arnie thought and I never asked him as he stood and watched the event from a safer distance.

The debris was real enough. Slabs of jagged ice protruded from the settled pack. It all looked very innocent in its beauty. But the weight and pressure was all I could think of and the relief that I had not been dragged under or pushed over. I was in little doubt the outcome could have been different. Miriam was indeed fortunate.

The rest of the run down through chamois tracks and narrow gorge trails was equally memorable as the Alps basked in their formidable winter glory. A stiff lunchtime refreshment in a Champagny restaurant saw off the trembles.

The next day I skied a second couloir with Serge in amazing snow. It sticks in the memory, along with a certain other event.