He was born in Valetta, Malta, but as a child moved first to Leicester and then to Bolton. After gaining a degree in biology from the University of York, he returned to Leicester and got a job at the University of Leicester in their Pre-Clinical Sciences department. Originally his writing was confined to songs and he didn't turn to fiction until he was 32. His first piece of work was a 250,000 word story about polar bears for his wife, Jay, to accompany a stuffed polar bear he had bought her as a Christmas present. He didn't write another story for seven years, until he heard about a competition to write a story for young children with a prize of 2,000. The resulting book, A Hole at the Pole, also about polar bears, didn't win - but he sent it off to a publisher, who accepted it.
His first children's novel, Fly, Cherokee, Fly, was published in 1998 and subsequently shortlisted for the Carnegie Medal. It was inspired by the time he found an injured pigeon in Victoria Park and nursed it back to health at home. It became a family pet and lived for 14 years in a birdbox attached to the back of the house. All of its offspring were given the names of different Native American tribes, which is where the title of the book comes from.)
He has since written over twenty children's books, including Pawnee Warrior (a sequel to Fly, Cherokee, Fly), a collaborative novel with fellow children's author Linda Newbery (From E To You), and the best-selling, award-winning The Fire Within series. His books often contain environmental themes, and events based on things that have happened to him. In July 2002 he was awarded an honorary doctorate from the University of Leicester for his contributions to children's literature. Although writing is now his main source of income, he still works at the university as the operator of the confocal microscope. His favourite children's books are the Paddington Bear series and The Hobbit, and his favourite children's authors are Allan Ahlberg and Roald Dahl.