Camps were struck on 20 July with no route having been selected but there remained the possibility of reaching the North Col from the east. Before heading that way, Mallory and Bullock started to investigate the place where, unknown to them, the East Rongbuk glacier debouches. They had to curtail their exploration here because bad news came that the photographs Mallory had taken were all useless because he had been putting the photographic plates in back to front. Photographs were vital as part of the reconnaissance so for two days Mallory and Bullock raced around retaking as many as possible. On this occasion Mallory re-took his photographs from Island Peak and Bullock actually reached the Lho La and was able to photograph the Khumbu Icefall. On 25 July they rejoined Howard-Bury's party at Chobuk.