Vertiginous views are one thing, but combine such dizzying prospects with the sense that the planks on which you walk might give way at a moment’s notice, and even the bravest soul would be forgiven for allowing a little fear to creep in. The urge to inhabit high up places has been with us throughout the course of human history – tied up with a desire for protection from predators and the ability to see threats coming from afar.