Diana Pullein-Thompson is the daughter of writer Joanna Cannan and Captain Harold "Cappy" Pullein-Thompson. She was part of a large literary family that included her maternal aunt May Cannan, a poet, and cousin Gilbert Cannan, a novelist-playwright. She and her three siblings all became writers. Along with her twin Christine Pullein-Thompson and other sister Josephine Pullein-Thompson, she is the author of many horse and pony books aimed mostly at girls, a genre established by their mother in the 1930s, which sold millions of copies. Diana also wrote books aimed at a slightly older audience, including some set in London. The sisters wrote a collective autobiography, Fair Girls and Grey Horses: Memories of Country Childhood. Diana has also published under her married name Diana Farr, including the biography Gilbert Cannan: A Georgian Prodigy (1978).