Last year, I hiked to Everest base camp – a tough and at times soul-destroying trek, especially when sub-zero temperatures meant there was no running water (I almost licked condensation off my teahouse window at one point, but that had frozen, too) and the thin air made my daypack feel like a bag of bricks. Even more soul-destroying was being overtaken by Croc-wearing sherpas who’d jog past us, carrying everything from freezers to satellite dishes on their backs.