Military attaché
Pereira had served as British Military attaché in Peking from 1905 to 1910 and was fluent in Chinese. He made many adventurous journeys in China and Tibet, frequently travelling thousands of miles on foot. He was the first European to walk from Peking to Lhasa, when he described the Amne Machin massif in eastern Tibet in 1921–2, sometimes reckoned among the great geographical discoveries of the twentieth century.