A charity stalwart is training for the toughest challenge of her life.

Siobhann Royce, from Stow-on-the-Wold, is planning to take part in a gruelling 250-kilometre endurance race to raise money for cancer patients.

The 29-year-old, a former pupil at Pate's Grammar School, will undertake the Marathon des Sables in memory of a close friend.

Sophie Drury, from Northleach, fought bravely against the disease for 10 years before she died last April, aged 34.

Through taking part in various marathons, triathlons and other fundraising activities, a group of Sophie's friends have contributed towards raising more than £107,000 for cancer charities.

And Siobhann is set for the most daunting challenge yet as she prepares to take on the Sahara desert.

Billed as the toughest foot race on earth, the Marathon des Sables will see her run the equivalent of six marathons in seven days in temperatures of 54C.

Siobhann, who works for a children's charity, said: "The Sahara marathon will without doubt be the toughest thing I have ever attempted.

"I am expecting it to shake me to the core.

"People have asked whether I am taking on too much, but I am a determined person and believe that if you set your mind to something, you can do it."

Participants in the annual event, which takes place in April, are expected to be self-sufficient for the duration of the race, carrying their own food, clothing and medical supplies.

They will have to face some of the most hostile conditions on earth including desert plains, sandstorms and sweltering temperatures.

Siobhann will be taking on the challenge with a team of five men. Together they hope to raise £100,000 for Macmillan Cancer Support.

She added: "We are dedicating our epic challenge to the vital work Macmillan nurses do to support cancer sufferers.

"It's an important cause which needs as much funding as possible, so we hope friends will dig deep to sponsor us. We want our efforts to have an impact on improving the lives of cancer patients throughout the UK – something Sophie would be proud of."

To sponsor Siobhann, go to www.justgiving.com/ SiobhannandNeal-Sahara Marathon2010. For more about fundraising work in memory of Sophie Drury go to www.sophieslegacy.org