Jenn Murray: I got cast in July, began in August, wrapped end of January. With Harry Potter, they had the novel to refer to, the people knew what was going to come up, people imagined them when they read them, but this is an original screenplay.

We did a read-through with all the actors in Leavesden Studios, and there were hard copies of the script, everyone was at a square table, and that was the first time I held it in my hand, and then you give it back as you leave.

The entire cast is so intelligent, and so lucky and happy to be part of the story.

The first day was really scary because we walked onto a big set, and Eddie Redmayne was there, and I've watched his work for years, I remember him from Tess of the d'Urbervilles, and when you look at someone's face, you want to hear their story, and he had that. and Samantha Morton, I had admired her for so many years because of her choices, she was a real actress - she took risks, she was very courageous, and you know nothing about her. It was magic, when you get those moments of 'This is great'.