His sister, Elinor May Monsell, won a scholarship to the Slade School of Art in London and became a painter, printmaker and illustrator, but Jack had no formal art training. Despite this, he became an illustrator, beginning with The Pink Knight, a story he had written, and illustrated in his notebook, to tell to a group of children. The publication of the book led to further titles such as Funny Foreigners, The Jingle Book, and Notable Notions all in 1905.