After the Garhwal trip, Graham and his companions returned to the Kanchenjunga area for the climax of their campaign; an attempt on Kabru, which Graham claimed to have climbed by the East Face in three days, reaching the summit on 8 September. After Kabru, Graham attempted several other mountains in the area, but the onset of winter prevented him from making serious progress on any of them. Kabru, at 7,349 m (24,111 ft), was far higher than any other mountain climbed at the time, and its ascent was and remains the most controversial aspect of Graham's expedition. Doubt was cast on whether he really had climbed this mountain or whether he had mistaken a nearby, lower mountain called Forked Peak (6,200 m, 20,340 ft) for Kabru. His ascent was doubted by members of the Great Trigonometrical Survey, whose maps of the area Graham had criticized in his June 1884 presentation at the Royal Geographical Society, and by a few contemporaries including Martin Conway and William Hunter Workman, both of whom had rival (lower) claims to the world altitude record. However, it was supported by climbers such as Norman Collie, Thomas Longstaff, Douglas Freshfield, and Carl Rubenson - Freshfield having travelled extensively in the same area himself and Rubenson having reached the same point on Kabru in 1907. In his 1955 history of Himalayan climbing Kenneth Mason argued that Graham had not climbed Kabru, pointing to the vagueness of his description of the mountain, inconsistencies between his account and modern observations of the mountain, the remarkably quick ascent he claimed, and the fact that he appeared to have suffered little or no altitude sickness on his ascent. In a more recent history, Walt Unsworth argued that the vagueness of Graham's account was to be expected from a man who was a mountaineer rather than a surveyor, and that now Mount Everest has been climbed in a single day without oxygen, Graham's claims seem less outlandish than they once did, so that he should perhaps be credited with the ascent after all. In a 10-page analysis in 2009, Blaser and Hughes argued that it is time to put the doubts to rest, and give Graham, Boss and Kauffmann their due credit for an extraordinary achievement.