Meet the woman putting her body on the line for Great Ormond Street Hospital, by running six marathons in five days through the scorching Saraha desert.
She must cover 156 miles across the sands of southern Morocco in 50C heat while carrying all supplies, except for water, on her back. The challenge is ranked by the Discovery Channel as the world's toughest foot race.
"The heat is my biggest fear but I'm doing lots of acclimatisation training in heat chambers at Kingston University and Silverstone," she said. "I knew I needed a really tough challenge to raise as much as possible for GOSH, because of the phenomenal work they do to help children around the world."
Ms Idris hopes to raise more than £10,000 for the hospital in Bloomsbury.
You can donate at www.justgiving.com/FearlessFarah and follow @Falanthropist on Twitter for updates on her training and the run itself.