Inspired by the children's historical novels of Geoffrey Trease, her first published book was "The Chronicles of Robin Hood" in 1950. In 1954, she published what remains her best-known work "The Eagle of the Ninth," part of a series on Roman Britain and its aftermath; they were not written as such or in sequential order but connected by the linking device of an emerald ring, passed down through generations of the same family. Between 1954 and 1958, Sutcliff's works "The Eagle of the Ninth", its sequel "The Silver Branch", "Outcast" and "Warrior Scarlet" were runners-up in the annual Carnegie Medal, given by the Library Association to the year's best children's book by a British subject. She finally won the Medal for her third book in the "Eagle" series, "The Lantern Bearers" (1959). Where the first two books and one subsequent one were set in Roman Britain, "The Lantern Bearers" immediately follows the withdrawal of the Roman Empire, when the British people are threatened by remaining Germanic troops and by invaders.