Trisul. The third ascent of Trisul (23,260 ft.) was made by R. D. Greenwood and Gurdial Singh of Dehra Dun on 25 June 1951. Greenwood, who is an instructor at the National Defence Academy, later climbed Ratanban (20,000 ft.) and also reached a point only 500 ft. below the summit of Mrigtuni Peak (22,490 ft.). Trisul had been climbed previously in 1897 and 1933.