Muriel Jaeger was born in Barnsley, Yorkshire. Her father was an accountant who changed the spelling of the family surname from Jagger to Jaeger, but why or when is unclear. She attended the Sheffield School, and in 1912 won a scholarship to read English at Oxford University. There she became a close friend of Dorothy L. Sayers and Winifred Holtby. The girls formed a writers' group that called itself the Mutual Admiration Society. After graduating in 1916, during World War I, Muriel moved to London for an administrative job in the government's Ministry of Food. She later worked for Time and Tide, a feminist journal, and Vogue Magazine, before becoming a full-time writer. Her first novel, The Question Mark, was published in 1926 by Leonard and Virginia Woolf's firm, Hogarth Press. She also wrote plays, popular history, biographies, and other nonfiction. Her science fiction works, such as The Man with Six Senses (1927) challenged the mindset of her era.