The Marathon des Sables has been described as the toughest race on earth. 849 competitors set off today on the gruelling six-day, 150 mile race across the Sahara.

"It was absolute hell", French runner Guido Di Paola said at the end of the first day, "as one had to walk nearly the whole time. You can only run a bit downhill but you have to be very careful. But with such an incredible setting, I don’t regret coming."