John Tiffany (director): All the seeds are there; we start with that scene in the train station. Am I allowed to say that? Anyway, it was clear that she was going to let us take those characters and have our own ideas.

Why a play? Was it J. K. Rowling’s idea?
Sonia Friedman (producer): It was absolutely Colin’s and my idea. We knew that many other producers had approached her and she had rejected their pitches. But that’s because they were all ideas about musicals or arena spectacles. We went to her with the simple idea of a straight play. We were clear we didn’t want to adapt a novel, and we suggested exploring how Harry, an orphan, would cope as an adult and a parent.

Colin Callender (producer): We went up to Edinburgh four years ago and sat in a boardroom and talked about fathers and parenting for a while. We said we felt she had created a fully dimensional world, and there were things about the characters she hadn’t revealed. We didn’t hear anything for a bit, then got the call to say, “Let’s go to the next stage.” She was clear from the beginning that she was not a playwright and wouldn’t write it, and that she would only do it if we found a playwright she approved.

You both share story credit with J. K. Rowling. How did it work having three writers in the mix?
John Tiffany: Jo Rowling was incredibly generous. I met her first, and I already had a soft spot for her because she used to write in the cafe of the Traverse Theater in Edinburgh when I was the director. It was only after the first book came out that I realized it had been her, nursing one cappuccino for four hours. When we met to talk about the play, she asked, “What do you think the Harry Potter stories are about?” I said, “Learning to deal with death and grief.” There was something in her eye — I thought, we didn’t say it’s about transformation or magic or flying on brooms, and we’re on the right track.

Jack Thorne {playwright): We all met in Edinburgh and as the day developed, we knew we would take the epilogue of “Harry Potter and the Deathly Hallows” as a starting point.

How is it different telling that story as a play rather than a novel?
Thorne: We can tell the story of the younger and older generation at the same time, which the books didn’t do. The exciting thing has been working out how those worlds fit together. It’s a coming-of-age story as much for the adults as for the children. John and I are more or less the same age as Harry in the play and I just had my first child, so there has been a lot of discussion about growing up, being a parent.

Tiffany: How do you mother or father when you still need parenting yourself?

Noma Dumezweni (Hermione Granger): Also, I think the difference with a play is that you’re not experiencing the story on your own the way you do with a book. Being in the theater is a communal experience, and this play, with two parts, is a commitment. I’m fascinated to see what my daughter will think after a whole day in the theater. As an actor, it’s something I’ve never experienced before.