An English-born writer of children's fantasy novels, she is best known for The Magician Trilogy and the Children of the Red King series. She earned a Nestle Smarties Book Prize for her 1986 work, The Snow Spider.
In her early adulthood, she worked for the BBC as a television writer. Her debut book, The Bronze Trumpeter, actually started out as a screenplay.
Her chapter books include the Delilah and Box Boys book series.
She was born in England and raised in Wales. She and her husband, David Millward, became parents to three children: Myfanwy, Ianto and Gwenhwyfar.
She and JK Rowling both won Nestle Gold Awards in 1997 in their respective categories.