In August 1870 Middlemore climbed Monte Rosa, the Strahlhorn and the Wetterhorn with guide Jakob Anderegg of Meiringen while qualifying for membership of the Alpine Club. In 1872 he made a traverse of the Matterhorn together with Frederick Gardiner and the guides Jean-Joseph Maquignaz, Johann Jaun and Peter Knubel of St. Niklaus in the canton Valais.