The author and Illustrator of such children's books as Baker Cat, Bouncing Buffalo, Tamara Drewe, and Gemma Bovery, she also worked as a newspaper Cartoonist. In 1977 she began publishing The Silent Three of St. Botolph's, a popular comic strip that appeared in The Guardian.
She studied at both the Sorbonne in Paris and the Central School of Art & Design in London. She published her first children's book, The Posy Simmonds Bear Book, in 1969.
The Academy Award-nominated animated short film, Famous Fred, was based on one of her stories.
She was born in Berkshire, England. She later settled with her family in London.