In the jungle highlands of Borneo, close to the modern border between the Malaysian state of Sarawak and the Indonesian territory of Kalimantan, the Kelabit people have always lived remote from the rest of the world. Their isolated plateau is high above the headwaters of the river system which is home to the rest of Sarawak’s indigenous people, and accessible only by several days’ trek through hazardous mountain passes. Their natural resources – particularly the succulent rice for which they remain famous, and the iodine-rich salt wells scattered across the plateau – made them comfortably self-sufficient. The first they knew of the modern world was in 1944, when a US Liberator bomber roared low over their plateau, and a gung-ho British anthropologist named Tom Harrisson descended by parachute into a world of hanging mist and thick, boggy sedge.

Harrisson was on a top-secret mission of his own devising, which had taken months to sell to his superiors.