Harry Potter and the phenomenally profitable franchise

It's 20 years since the first Harry Potter film was released and the movies and books have spawned a world of wizard-related retail opportunities. Elizabeth Hotson asks Chris Columbus, director of the first two Harry Potter films, how he dealt with the pressure of bringing the boy wizard to life. And we travel to Edinburgh for The Potter Trail tour which starts with a spell and ends in a graveyard. We step inside the magical Museum Context shop, and hear form owner, Andrew McRae. Plus, Scott Mendelson, a film critic and box office pundit at Forbes, tells us why he thinks the franchise has been so successful. And we end with a look at the most hallowed of magic artefacts, the philosopher's stone itself.Presenter: Elizabeth Hotson Producers: Elizabeth Hotson and Sarah Treanor(Picture of a boy dressed as Harry Potter, Picture by Stephen Chernin for Getty Images)