When Kinthup was being trained for the Tsangpo mission, a Chinese lama was staying in Darjeeling. He had a passport to Tibet. Moreover, he could read and write; Kinthup was illiterate. So it was decided that Kinthup would go into Tibet disguised as the lama’s servant. The Chinese passport would give them free access there, the lama would also assist Kinthup to keep the survey records.

Though he couldn’t read and write, Kinthup had mastered the basic skills of topographic survey and the working of instruments. He also had an amazing memory. The two men set out from Darjeeling on a wet afternoon in July 1880. Kinthup was leaving behind his wife, two young sons and a newborn daughter in a tiny shack in Butcher Bustee. The code of espionage forbade him to share with anyone the details of his mission, which was expected to be completed in four months. . . .