On 7th June 1924, George Mallory, a 38-year-old English schoolmaster, and Andrew Irvine, a 22-year-old university student, stopped to rest on Mount Everest at 26,800 feet, before making the final ascent.

The next morning, they set off on the most difficult and dangerous stage of the whole climb, and around midday they were seen for the last time. In 1999, Mallory's body was found, mummified. What clues did it give to the last moments of the intrepid explorers and how far they climbed?