A lost climber, a missing camera and fears of an astonishing Chinese conspiracy to hide the truth: Mountaineer charts intrepid attempt to force Everest to reveal final secret after 97 years

From far below, they were two tiny dots close to the summit of the world’s highest mountain. It was just before 1pm on June 8, 1924 and the dots seen by geologist Noel Odell were George Mallory and Andrew Irvine, soon to be lost in a ferocious snow storm.