On 31 July 1876 Middlemore made the first ascent of the north-east face of the Aiguille Verte by what is now known as the Cordier Couloir with the London stockbroker John Oakley Maund, the Chamonix guide Henri Cordier, Grindelwald guides Johann Jaun, Andreas Maurer, and Jakob Anderegg. The route was not repeated until 1924, and according to Helmut Dumler is one of the most respected achievements in the history of mountaineering, for the 900m couloir is set at an angle of up to 56°. Engel notes that the party were all nearly obliterated by rockfall while they were crossing the bergschrund.