Marguerite Steen was adopted as a child and educated at a private school and at Kendal High School. At age 19, she became a teacher, but abandoned that career after three years and moved to London in an effort to find work in the theater. After failing at that, she became a dance teacher in the Yorkshire schools. This job enabled her to spend long periods travelling in France and Spain. In 1921, she joined the drama company of Fred Terry and Julia Neilson, based at The Strand Theatre in London, and spent three years touring with them. She was befriended by Fred's sister Ellen Terry, who suggested that she try to write a novel during a period of unemployment. Marguerite's first book, The Gilt Cage, was published in 1927. She went on to become a well-known author of some 40 books, mostly historical novels, having her greatest popularity in the 1930s and 1940s. She wrote biographies of the Terrys and of her friend Hugh Walpole, as well as that of 18th-century writer and actress Mary Robinson. Among her bestsellers were Matador (1934), for which she drew on her love of Spain, and The Sun Is My Undoing (1941). She also produced two volumes of autobiography, Looking Glass (1966) and Pier Glass (1968), which provide insights into the English creative set of the 1920s to 1950s. She shared a home with artist Sir William Nicholson for about 15 years and wrote his biography as well. In 1951, she was elected a Fellow of the Royal Society of Literature.