According to Claire Engel, Middlemore was one of the first alpinists to climb routes in the Alps of an unprecedented degree of difficulty and danger: Middlemore's crossing of the Col des Grandes Jorasses made his Alpine Club colleagues realize that mountaineering had found a new mode of expression. With his guide, Jaun, and their porter he spent his time dodging falling stones ... One wonders here at the extraordinary lack of foresight displayed by both Middlemore and his guide, or at the indifference to the most elementary rules of prudence.