On June 8, 1924 George Mallory and Andrew Irvine attempted to climb to the top of Mount Everest via the North Col route. Keen-sighted expedition colleague Noel Odell reported seeing them at 12.50 p.m. ascending one of the major "steps" on the ridge and "going strongly for the top" but no evidence thus far has proved conclusively that they reached the summit. They never returned to high camp and died somewhere high on the mountain.
http://en.wikipedia.org/wiki/George_Mallory

thanks for the idea to HughC