Hart was known for his diplomatic skills, and befriended many Chinese and Western officials. This aided him in directing customs operations without interruption even during periods of turmoil. His American Commissioner, Edward Drew, credited him with preventing a war with Britain in 1876 (via the Chefoo Convention), and he and his London representative, James Campbell, helped bring about peace after a French attack on the Chinese navy in Fuzhou in 1884. In 1885, Hart had also been asked to become Minister Plenipotentiary at Peking, upon the retirement of Sir Thomas Wade. He declined the honor after four months of hesitation, on the grounds that his work in the Customs Service was of certain benefit to both China and Britain, but that the outcome of a change of post was unclear.