Although well-known early in the century for his drawings and etchings the bulk of John’s later work consisted of portraits. With his vivid manner of portraiture and his ability to catch unerringly some striking and usually unfamiliar aspect of his subject, by the 1920s he had superseded Sargent as England’s leading portrait painter.

John’s work has been offered at auction multiple times, the record price being 487,500 USD for Head of a Girl sold at Christie’s in 2021.