American endurance athlete Tyler Andrews’s record-breaking Everest ascent has triggered a fierce debate in the climbing world, with critics questioning whether his 9-hour, 55-minute summit push from Base Camp benefited from an earlier “route recce”.Andrews’ original goal had been to break the no-O2 Everest speed record and he had left Base Camp on May 23, but shifting weather and complications forced him to use bottled support before he turned back. Critics said the climb helped him study key sections, plan his speed push and acclimatise.