The 1921 British Mount Everest reconnaissance expedition set off to explore how it might be possible to get to the vicinity of Mount Everest, to reconnoiter possible routes for ascending the mountain, and – if possible – make the first ascent of the highest mountain in the world. A feasible route was discovered from the east up the Kharta Glacier and then crossing the Lhakpa La pass north east of Everest. It was then necessary to descend to the East Rongbuk Glacier before climbing again to Everest's North Col. Initially the expedition explored from the north and discovered the main Rongbuk Glacier, only to find that it seemed to provide no likely routes to the summit. However, at the time it was not realised that the East Rongbuk glacier actually flowed into the Rongbuk glacier – it was thought it descended away to the east. As a reconnaissance the expedition was a success because it determined that a good route might be to approach the East Rongbuk glacier via the Rongbuk glacier, and then follow the North Col route to the summit.