Roald Dahl is thought by many to be the greatest children's writer of all time. His books have sold hundreds of millions of copies the world over and are still being made into Hollywood movies and West End musicals. But few people know that Roald Dahl was Welsh: born and raised in and around Cardiff in the 1910s and 20s. These early years were crucial for the man and the writer, helping to shape the course of Roald Dahl's entire life. This programme tells the untold story of the Roald Dahl's Welsh childhood, full of mischief and magic, but also sadness. We discover how books like Matilda and James and the Giant Peach were influenced by their author's school days. We delve into the tale of the Great Mouse Plot and get a taste of a family home described by friends as a madhouse. And we look at the darker side of Roald Dahl's young life - the loss of a sister and a father, and being sent away from the mother he loved. With contributions from Roald Dahl's wife Felicity 'Liccy' Dahl, Horrid Henry author Francesca Simon and biographer Donald Sturrock.