Julian Trevelyan was the nephew of the historian G.M.Trevelyan. While at Cambridge reading English Literature he became interested in French art and Surrealism. In 1931 he moved to Paris and studied at S.R.Hayter’s school Atelier Dix-Sept, where he learnt the techniques of etching and met Max Ernst, Picasso and Joan Miro. In 1935 he settled in Durham Wharf in Hammersmith, where he lived and worked for the rest of his life. In 1936 Trevelyan became a member of the Surrealist Group and participated in the International Exhibition of Surrealism at the New Burlington Galleries. In 1937 and 1938 he was involved in the Mass Observation movement, which stimulated his interest in industrial landscapes as subjects.
During the Second World War Trevelyan worked as a camouflage officer. In 1951 he and his second wife, Mary Fedden, painted a series of murals for the Festival of Britain. He was a member of the London Group from 1948 to 1963, becoming its vice-president in 1956. From 1950 to 1955 Trevelyan taught etching and history of art at Chelsea School of Art, and from 1955 to 1963 was tutor in engraving at the Royal College of Art, eventually becoming head of the Etching Department. His pupils there included David Hockney. In 1986 he was awarded a Fellowship of the Royal College of Art, and in 1987 became a Royal Academician. Trevelyan was also a writer on art, and in 1957 published his autobiography, Indigo Days