Scott had a vision. Amundsen had a dream. This is how inspiration to conquer the Antarctic took former maths teacher and head Dorothy Dalton. “I was on an expedition in the Andes. We were about to cross into Chile. It had snowed and it was very cold. I was outside in the morning, squatting down with the snow falling on my bare bottom, and suddenly the idea came to me. Why didn’t we try to have a group of women, all aged over 50, make an attempt to walk to the South Pole?”

This was not the first exciting idea Mrs Dalton, 54, had had. Twenty years ago, with two small sons, she was teaching maths part-time at Harrow school, where her husband, Bill, is still on the senior management team.

She felt under-occupied, so set up a charity, which she called Jolt (Journey of a Lifetime Trust), to take disabled and deprived teenagers on international expeditions. “I had always loved to travel and I thought young people who had a major disadvantage could gain a great deal.”

Contacting social services, local education authorities, schools and charities, she selected 15 youngsters in difficult circumstances and escorted them through Siberia, Mongolia, and China to Hong Kong. The trip, and its nine biennial successors going to South America, Asia, Africa and the Middle East, was not without problems. “We had a 17-year-old girl tell us she was three months pregnant in the middle of Mongolia, and a boy who managed to buy black hash in Siberia and pass it to one of the others in his group.”

But the overall effect on Jolt voyagers was astonishing: “If you are in the middle of nowhere and you have a crisis, you cope because you have no choice. By working together, by supporting each other, it’s amazing what these young people can do. Someone paraplegic can be the eyes for someone who is blind. If they can get through an expedition of that kind, they can cope with what life throws at them.”

After the fifth Jolt expedition, and by this time headteacher of Northwood secondary school in the London borough of Hillingdon, Mrs Dalton decided it was time for a more personal challenge. So she organised an all-women fund-raising trip for Jolt, white water rafting down the Zambezi. “I am a physical coward and I thought I should see what it felt like to do something more challenging. There were terrifying moments - like when one of our kayaks was attacked by a hippo - but we survived.”

The trips fell into a pattern: one year a Jolt expedition, the next fundraising - until her Antarctic moment in the Andes. She was facing 50; she wanted to prove “that at an age when people are thinking of retiring or slowing down, a group of women with no history of exploration or mountaineering or long-distance skiing could, with the right motivation and working together to support each other, complete a very challenging and arduous expedition”.

Since then, her eyes, and those of the nine friends she has recruited, are fixed firmly on October 2004, when they will set out to ski 730 miles, travelling from the edge of the Antarctic to the South Pole in aid of Cancer Research.

The Spirit of the Age expedition will, she says, be far tougher than any of her previous ones. “We will be moving for five to eight hours a day, skiing and pulling sleds, in temperatures as low as - 40C, in one of the hardest environments in the world.”

The expedition team includes several senior charity and civil service executives - Mrs Dalton now works as a charity consultant, having left teaching 10 years ago - as well as journalists, midwives and nurses. Many have families: Mrs Dalton’s two adult sons, one in the middle of a PGCE, are supportive though worried, she says. For her husband, not a keen traveller, “this is one trip too far”.

The expedition team has begun regular joint training sessions, recently camping out in - 27C in Sweden, learning crevasse rescue techniques. Early next year they will ski across Iceland. As well as physical workouts - Mrs Dalton does hers in the Harrow school gym - they know they must prepare mentally, not only for the expedition strain but also for the non-hierarchical leadership structure (an innovation in the face of Scott-style heroics) which they hope to sustain. “We’re a group of stroppy women. We are all used to taking risks, but also to being in control. We need to turn that into something positive: into a shared leadership in which we work together as a team.

“At times I think it will be horrendous: the sensory deprivation, the lack of landmarks, the daylight all the time. But I am looking forward to it.

I’m looking forward to getting to the South Pole, but I’m also looking forward to the learning. This is the teacher in me. I believe life is about learning and doing new things.”

The Jolt Trust: www.jolttrust.org.uk.To follow the progress of the Spirit of the Age expedition: www.redhouselane.co.uk spirit_of_the_age