As well as their climbing achievements their story is one of an extraordinary 47 year friendship that defied the rigid class conventions of Victorian Britain. Despite their different backgrounds they were bound, like the rope that they slung between them, by a common love of Skye’s wildest places. Collie may have climbed in the Alps, Norway, the Himalayas and the Canadian Rockies but it was Skye and the memory of his friendship with Mackenzie that he would return to at the end his life.
The more Sara looked into mosses and lichens, the more fascinated she became by their story of dogged survival in the smallest of ecological niches. “When you focus on just one part of the ecosystem you realise that it has its own world to it,” she told me. “It may not have the drama of the African savanna but it is no less important.”