Boyle and Dear both came up with the idea of alternate casting. “It makes sense,” says Boyle. “These two characters, in many ways, they’re the same person. In this adaptation, they’re the creator and son, and the obligation in that relationship is very close. I was quite keen to have an actor that I knew and one that I didn’t. I’d worked with Jonny on Trainspotting [he played Sick Boy], but not Benedict. They’re of similar ability, but they come from different traditions – which seemed right.”