Enter the magical world of children’s writer Cressida Cowell. She created the hugely successful How to Train Your Dragon series, which continues to excite children across the globe and has been turned into Oscar nominated animated films. For her latest series, Cressida explores teenage magic and Iron Age warriors. As she works on the illustrations for the second book in this new trilogy, The Wizards of Once: Twice Magic, she gives fellow children’s author Michael Rosen an insight into how she creates these worlds.