“MUMMY, are you going to die?” asks five-year-old Zachary Marsh, and his mum fights back her tears.

Ros Marsh deals with most things in her life in a matter of fact way. She has beaten breast cancer, run the New York Marathon, trekked to Machu Picchu and cycled from London to Cambridge to raise more than £80,000 for charity - this is not a woman who struggles to cope.

But when her children ask the question that matters most, she feels helpless.

Because the answer is yes. At 42, Ros has Stage 4 bone cancer and she is going to die - long before Zachary grows up. Scans have shown the cancer is aggressive and terminal. She may have a year, possibly two, but how can she tell that to a five-year-old?

“The hardest part of all this is dealing with my little boy,” says Ros, tearing up as we chat in the conservatory of her Broome Manor home.

“He knows I’ve got a bad back. We tell him I’ve got special nuggets in my spine that are making me poorly, but he still asks some soul-searching questions.

“We are very gently drip-feeding him information, but he’s not silly. He puts two and two together.”

Teenage daughter Sophia, 16, obviously understands more. This is not the first time she has seen her mum battle cancer. She was only five herself when Ros found a lump in her breast, which was quickly confirmed as breast cancer. Ros had a double mastectomy and reconstruction surgery at the age of 30, followed by chemo and radiotherapy.

Within weeks of her op, she was taking part in a Three Peaks Challenge in the North Yorkshire Dales, walking 26 miles at more than 5,000ft. “People told me not to, but I needed something to focus on,” she said. It must have worked, because she beat the cancer and was given the all-clear a few years later.

She went on to have another child, Zach, despite being told it was improbable she would conceive, and to marry his dad, Roger.

It’s her strength and defiant attitude that have earned her a place in the final of the Woman Of Courage Awards 2009, run by Prima magazine in conjuction with Breakthrough Breast Cancer.

Friend Amanda Woodhead, of Wroughton, nominated her, saying: “I am humbled by her amazing outlook and generosity. She has bundles of enthusiasm and a zest for life. She just never stops.” Enthusiastic is a word that could have been invented for Ros.

Following her diagnosis with breast cancer she joined the Wiltshire Breakthrough Breast Cancer group and has spent the past decade dreaming up more and more adventurous stunts to raise money for her friend Shirley Garman. Terminal patient Shirley’s last wish is to hit the £1m mark with her fundraising.

In fact, it was shortly after picking up an award on Shirley’s behalf that Ros realised she was ill again herself.

“I went to an awards ceremony because Shirley was too ill to attend. What I didn’t realise at the time was that I was too,” she said.

“Last October I felt a muscle spasm in my back - the doctor thought I had just pulled a muscle. Two weeks later I had an enormous spasm that put me in a wheelchair. I think I knew then that something wasn’t right.”

Doctors ordered a bone scan, suspecting Ros had a broken rib. A few days later, she answered her phone in the car and the doctor told her to pull over. The tests had proved “not entirely normal”.

This time, Ros has decided not to have chemo, feeling its detrimental effects are not worth the small amount of extra time it may give her.

Instead, she is focussing her time and attention on the people she loves - and on living life to the full. She recently took 29 members of her family on holiday to a chateau near Paris and has been to Dubai and Disneyland Paris with her husband and children. She has a host of nights organsied to raise even more money for charity, and is busy planning a family ski trip.

“I am now spending time with all the people who matter to me - my family and friends,” she said.

“I want to live my life with things to look forward and to create memories of happy events.

“But I’m not planning anything beyond December at the moment. After that, we’ll see . . .”