She has cycled 2,500 miles from Rome to her home in Leeds, competed in a gruelling triathlon in Florida and raised more than £1m for charity - while living with terminal cancer. The inspirational Jane Tomlinson tells Women's Editor Lindsay Jennings why this year, she'll be watching the London Marathon at home.

JANE Tomlinson had already taken part in a marathon, three triathlons and a 2,500-mile tandem cycle trip across Europe when she decided to enter one of the most gruelling competitions in the world.

But the prospect of the Full Ironman Triathlon in Florida - a 2.4-mile swim, followed by a 112-mile bike ride and 26.2 -mile marathon - while suffering terminal cancer left even her a trifle daunted.

"The whole thing when you think about it is a little scary," she says, in her typical understated way. "The fact that it was sea swimming all that way, but I kept breaking it down and saying 'I'll see how I feel when I get out,' then I'd get on the bike and think 'this is awful, should I stop?' but then I'd carry on and think I'll do another ten miles and see how I feel. Then once you've gone so far you think there's no way, unless I really can't put one foot in front of the other, that I would stop."

It is this determination, to put one step in front of another when faced with such adversity, which has seen Jane, 41, become an inspiration to millions. She has defied doctors, who predicted four years ago that she only had months to live, and gone on to achieve sporting feats which people without a terminal illness would struggle to complete.

She was first diagnosed with breast cancer aged 26, when she was married to Mike and living in Rothwell, Leeds, with her two daughters Suzanne, now 19 and Rebecca, 16. It was successfully treated with a mastectomy and chemotherapy and she went on to train as a paediatric radiographer before having third child, Steven, now seven.

But the cancer returned in 2000, invading her bones and lungs and she was told to start thinking in the present, not in the future.

''I felt myself thrown against a brick wall," she says. "There was no way forward, this was how my life would end. My breath felt punched out of me by the shock.

''I imagined a gaunt, pale figure lying in bed, her eyes sunken and her cheek bones prominent, her wrists painfully thin. It terrified me.''

Jane decided she needed some goals - but no-one could imagine the challenges she would set herself. Astonishingly, she had never tried long distance running before, let alone competed in marathons.

"It was just one of those things which happened," she says simply. "I started running and I enjoyed it and I wanted to set myself something to do."

She began with the London Marathon in April 2002 and went on to cycle from John O'Groats to Land's End and complete a 2,500 mile tandem cycle ride from Rome to Leeds with her brother, Luke Goward. In November she became the first terminally-ill cancer patient to complete the Full Ironman triathlon in Florida - a feat she completed in 15 hours 48 minutes, topping up on her painkillers as she went.

Her efforts have raised more than £1,150,000 for cancer charities and saw her receive an MBE and the Sports Personality of the Year's Helen Rollason award in December 2002.

"I'd been well and truly set up," she says, laughing at the way her family had been in on her BBC award, recording poignant messages for the video clips which were played before she received it. "It was a fabulous evening. The best thing about the things I've done has been some of the experiences we've had and some of the memories the children will take away from them. The biggest thing was that my family was there to see it."

But there have been those who have questioned why she would choose to focus so heavily on the events and personal challenges when she could be spending every minute with her family.

"My eldest daughter is at university and if I were to sit at home doing nothing then should she be sitting here with me?" she says. "That's not the way we live our lives. I have to balance what I do with my family, but I don't think it detracts who I am as a mum.

"I'm a charity fundraiser that people know well and when I go home and shut the door, I'm just Jane Tomlinson, a mum, a wife and a daughter."

Part of her motivation all along has been to give hope to others, particularly families who may be in the same situation.

''I want to show somebody who might have a similar prognosis that you can set yourself goals, that it doesn't matter if it seems a bit impossible, set yourself a goal and aim for it and get on with it," she says.

''I try to give myself something to aim for. Short-term goals, trying not to think too far into the future. The one thing I do pray for is a calmness, to feel that when the time has come, to know it's my time and to be at peace with that idea.''

Mike, an IT consultant, has been there throughout, constantly supporting all her goals. It was important to both of them, she says, that they wrote their new book The Luxury of Time together, before someone else decided to. There had already been offers for people to ghostwrite their story.

"I felt that if we didn't write something then someone else might and we wanted it to be our account of what's happened and for other people to understand what it's like if they're ever faced with that situation," she says. "It's saying to people that it is manageable. We don't go home every day and shut the door and say "it's grim here" because I'm feeling unwell. You don't have to be miserable about it, you can get on with your life."

Nor does she have doubts about Mike's ability to cope when she is no longer here.

''When I met Mike we both chose to spend our lives together. We have a family together and I trust Mike to make the right decisions about the future.

''I can't sit here and make a prescriptive list about how he should bring up our family when I don't know what circumstances they will be in. And if I didn't trust him to bring up my family to the best of his ability, then I wouldn't have chosen to get married.''

The couple have always been open with their children about her condition. She felt it was important to make it possible for them to speak to her about it rather than hide away from the truth about her illness.

"It's how we feel, that the children have most confidence in knowing what's going on," she says.

Jane continues to work as a paediatric radiographer at Leeds General Infirmary and is halfway through another bout of chemotherapy. The cancer has spread to her bones in her lower back, her hips and pelvis.

"It's always very difficult when you have to face the choice: do I think I can manage another six months of feeling unwell or is it time to say that's enough now?" she says.

''I've been very lucky that I've had very good reactions to the chemotherapy. It's not stopped the disease but it's slowed the progression down and it's allowed me to stay positive."

The chemotherapy also means she has to listen to her body more, and rest when it tells her to. The only marathon she will be enjoying in the near future will be the London Marathon - from the comfort of her sofa and with her family around her.

"I may even have a full English breakfast," she laughs. "Just because I can."

* The Luxury of Time, by Jane and Mike Tomlinson (Simon & Schuster, £16.99). A documentary - Jane Tomlinson: Fit For Life - is on BBC1 tonight.