"Gary actually came around the next morning, because we lived near each other at the time, and he said, 'Have you seen the new book? We've got a lot of work to do, mate.' He was quite happy, and I didn't know how to break it to him. So I said, 'Have you actually read it yet, Gaz?' 'No, just flicked through it.' A few days later I'm in makeup and he comes in and sits down and goes, 'Have you heard the news?' 'What's that, Gaz?' 'It's terrible fucking news' 'What is it?' 'You know how everyone is talking about who dies in book five? It's fucking me! This woman puts the poor bastard in prison for 12 years, brings him back for a few scenes, and then she kills him!'"
David Thewlis on Gary Oldman finding out Sirius dies in ‘Order of the Phoenix’