A 57-year-old charity chief executive led 10 runners in a 150-mile fundraising race in temperatures up to 42deg Celsius in the Sahara desert.
Jo Williams, chief executive of Mencap, and three of her colleagues failed to finish the Marathon des Sables in Morocco.
In what is known as the toughest race on earth, participants have to run with their possessions in rucksacks over uneven ground.
Williams quit at stage three, 50 miles into the event. "I gave the event my best shot, but unfortunately the high levels of humidity proved really challenging," said Williams, who had previously run seven marathons.
The Mencap team hopes to have raised £60,000, which will go towards a new respite centre for children aged eight to 14 with profound learning disabilities. Of 731 people who started the race, 146 failed to finish it.