When Clare Dean sets out to trek towards the Choquetacarpo pass in Peru in two weeks’ time, every step she takes will be a triumph for her indomitable spirit, for modern medicine, and for her aim to spread the word that these days there is life - a whole heap of it - after cancer.

Clare, deputy news editor of The TES, was first diagnosed with cancer in 1990. Since then, she has undergone surgery, chemotherapy, and, when the disease returned six years later, more chemotherapy, radiotherapy and a mastectomy. Now she’s using her story and her contacts in education to raise awareness about cancer - and money to help beat it.

For her 12-day trip to Peru, a fundraiser for Cancer Research UK, she will be accompanied by 49 other trekkers supported by guides, porters and a mobile camp. But before she tackles the Andes, Clare is undertaking a mini-tour of British schools and teacher union conferences. This weekend, for example, at its annual conference in York, the National Association of Head Teachers will for the first time hold an official collection for charity.

“It’s a very worthwhile cause,” says incoming NAHTpresident Gareth Matthewson, head of Whitchurch school in Cardiff. “Anyone who works in an educational setting, even if it’s not directly in a school but indirectly, like at The TES, knows about setting an example in thinking about others, and Clare’s a great friend of ours. We’ve never done anything like this before, but she got us at a weak moment - and anyway, she probably wouldn’t have taken no for an answer.”

The NAHT is following the example of last year’s conference of the National Association of Schoolmasters Union of Women Teachers, where delegates poured money into Clare’s hands. “I went back to my hotel room with wodges and wodges of cash,” she says. The amount almost hit four figures.

Then there are the schools. Two headteachers - Alan Stockley of Landywood primary school in Walsall, Staffordshire (see panel), and Simon Marsh of St Mary Magdalene CE primary in the London borough of Islington, both NAHT council members - have invited Clare into their schools, where she’s talked about her illness and her coming adventure and encouraged the children to raise money for Cancer Research UK.

Clare was 40 last year. “That’s when it hit me,” she says. “I realised I’d thought I wouldn’t get there. I hadn’t said it to anyone, I hadn’t even said it to myself, but I really hadn’t believed I would make it. And when I did, I thought, ‘Well, I’ve spent 13 years living with cancer. So maybe now I can do something to help other people.’ I feel so lucky. Honestly.”

But luck would not be the word that springs to most people’s minds as they listen to her story. At 28, shortly after she joined The TES as a reporter, she found a lump in her armpit and was diagnosed with secondary cancer.

Over the next five months she had four operations, all of which failed to find the primary problem. She was referred to the Royal Marsden hospital, “where I was deemed an interesting case, which is not really something you want to be. At one time, I had five or six doctors looking at me, along with others from overseas. I said I should have sold tickets.”

They never did find the original cancer. Instead, Clare had a course of chemotherapy and went on her way until, six years later, she found a lump in her breast - “I knew straight away what it was” - and was whipped back into hospital, first to have the lump out, then, when it returned, to have a mastectomy, followed by chemotherapy and radiotherapy. She returned to hospital in 1999 for a six-hour reconstruction operation, which involved muscle tissue from her stomach being pulled up to fashion a new breast.

“I’m held together by mesh,” she says. “I can’t ever put on any weight because I can feel it starting to get tight.”

Although she makes light of it, it is the kind of medical journey that would have floored anyone with smaller reserves of optimism and energy - which is probably just about everyone. The operations left her scarred. The chemotherapy made her vomit so much she carried a small bowl whenever she went out. She didn’t lose her hair, but she lost her eyelashes. She was tired from the treatment. Sometimes she was scared. And in the run-up to her six-monthly check-ups, she still gets anxious and edgy.

So where is the luck in that? Clare ticks off a long list. Her parents, her family, her friends, her colleagues. Her space-scientist husband, “who took me on in the middle of all this, and who has been through everything with me”. Her employers, who have been, she says, supportive and caring. The consultants and nurses at the Royal Marsden. Her rebuilt body - “It’s fantastic. I only have the very best underwear now. You have to do what makes you happy” - and the way that living with cancer has shaped her attitude to life.

“I’ve always been a positive person, but I’m much more so now. You’ve got to appreciate everything you’ve got and everything around you. You’ve got to make the best of what you’re doing, and see the best in the people you’re doing it with. And there is so much kindness and generosity around.

I can’t believe it.”

Her trip to Peru will involve six to eight hours’ steep mountain walking every day, for which she has been preparing with regular workouts at the gym. It will also mean travelling with strangers, and sharing a tent with someone she has never met. And it has catapulted her into new challenges, such as learning Spanish, and doing public speaking as part of her fundraising. At home, in Oxfordshire, and in Warwickshire, where her parents live, there have been coffee mornings, a concert, a barbecue for her father’s golfing friends, and a boot sale. “Everything they say about boot sales is true. I wore my market trader’s outfit: a denim mini skirt and a bum bag. It was hard work, but we raised pound;275.” At work there has been a pub quiz, a donation from the company, and sponsorship from colleagues.

Clare has already raised more than pound;5,000, double her target for the trip, and says: “I’ve been overwhelmed by people’s generosity and humbled by people’s kindness. And I’ve been amazed at the number of people who have been touched by cancer, either because they’ve had it, or because someone among their friends and family has been affected.”

Which is something The TES as a whole knows better than it would like to.

One in nine women will get breast cancer at some time in their lives, although most will be well over 50 when it happens. Yet the incidence at The TES - where people are much younger - is far higher. Over the past few years there have been five cases among fewer than 30 women on the editorial side of the paper, plus others among associated freelance writers.

And although treatment is so good now that most are well and working, everyone on the paper is acutely aware of how it remains a frightening subject - for adults, never mind children. Which is why the whole office is rooting for Clare as she shoulders her backpack and heads off for South America. And why Clare herself says: “We still call it the big C. But we should be calling it the small c, the lower-case c. I want to say to people, ‘Cancer doesn’t automatically equal death. Look at me. You don’t have to be so scared of it.’”

To make a donation, or to book Clare to speak in your school, contact her on 07860 951410, or email trek@tes.co.uk