Eva Ibbotson was born in Vienna, but when the Nazis came to power her family fled to England and she was sent to boarding school. She became a writer while bringing up her four children, and her bestselling novels have been published around the world. Journey to the River Sea won the Nestlé Gold Award and was shortlisted for the Carnegie Medal, the Whitbread Children's Book of the Year, and The Guardian Children's Fiction Prize. Some of her other young fiction titles include The Great Ghost Rescue, Which Witch? and Dial a Ghost. Eva passed away in October 2010 at the age of eighty-five. Sibéal Pounder used to work for the Financial Times, where she researched the How To Spend It section and wrote the For Goodness' Sake column - interviewing everyone from Veronica Etro to Vivienne Westwood. Now she writes about fabulous witches and bad mermaids in her two much-loved series for Bloomsbury. Sibéal's first book, Witch Wars, was shortlisted for the Waterstones Children's Book Prize 2016.

Beatriz Castro was born in La Rioja, Spain in 1985. When she was a little girl, she was always drawing and writing stories. She studied illustration at the school of arts in her home town, Logroño. After graduating, she embarked on a career as a professional illustrator and has since been published by many international publishing houses. She especially enjoys creating funny characters. Beatriz likes animals, classic stories and fairy tales and listens to rock and punk music.