Watson was born in Derby, England, but moved with his family to Brazil, where his father managed a sugar-making plant.
Here he intercepted German radio traffic for dispatch to Bletchley Park, and later interrogated Japanese prisoners of war, developing a passion for Asian languages.
In 1954 he spent a year in Japan, where he encountered classic Japanese painting and sculpture, met leading scholars, and acquired a working knowledge of the language and writing.
Under Watson's guidance this focused on the approachable, mainly secular, art of the Edo period, with both exhibition and catalogue produced by British specialists, rather than being simply imported from Japan.
His last work, the final book of a three-volume set on China for the Pelican History of Art series, was published shortly before his death.