In 1945, she chose the pseudonym "Jean Plaidy" for her new novel "Together They Ride" at the request of her agent. The name was inspired by Plaidy Beach near the Hibberts' home in Looe, Cornwall during World War II. Her agent suggested the first name, saying ""Jean" doesn't take much room at the back of the book". The book was published by Gerald G. Swan, a London publisher. The next book written under the "Jean Plaidy" pseudonym was "Beyond the Blue Mountains" in 1948. The publisher Robert Hale accepted the 500-page manuscript after it had been rejected by several others. The firm wrote to Hibbert's literary agency, A.M. Heath, "Will you tell this author that there are glittering prizes ahead for those who can write as she does?". In 1949, Hibbert hit her stride with the first "Jean Plaidy" novel that fictionalized stories of royalty: "The King's Pleasure", featuring Henry VIII and Anne Boleyn. A total of 91 "Jean Plaidy" novels were published. Hibbert's last "Jean Plaidy" book, "The Rose Without a Thorn", was published posthumously.