As an important contributor to the pop art movement of the s, he is considered one of the most influential British artists of the 20th century. Hockney has owned a residence and studio in Bridlington and London, as well as two residences in California, where he has lived intermittently since one in the Hollywood Hills , one in Malibu , and an office and archives on Santa Monica Boulevard  in West Hollywood , California. He was associated with the movement, but his early works display expressionist elements, similar to some works by Francis Bacon. When the RCA said it would not let him graduate if he did not complete an assignment of a life drawing of a female model in , Hockney painted Life Painting for a Diploma in protest. He had refused to write an essay required for the final examination, saying he should be assessed solely on his artworks. Recognising his talent and growing reputation, the RCA changed its regulations and awarded the diploma.