I. Bonnington is now Britain's best known mountaineer. II. The book he wrote about the journey was a best-seller. III. He is not, perhaps, as famous as Edmund Hillary, who was the first man to have conquered the world's highest mountain. IV. But he was the first to reach the top via Everest's previously unclimbed South-West Face. V. This route had already been attempted on six occasions bur on each occasion the result had been a defeat.
Which one is irrelevant?