Sir Ranulph Fiennes

The famed explorer is taking on arguably his most grueling challenge yet - a 56-mile run in the 50-degree heat of the Moroccan desert.

71-year-old explorer is aiming to become the oldest Briton to complete the Marathon des Sables to raise money for charity.

The British explorer will travel across Antarctica during the southern winter, where temperatures can plummet to -90C.