Sally Rooney has said the biggest challenge of adapting her hit book Normal People for the screen was translating their inner lives into outward actions.
The novel follows the relationship between Marianne and Connell from the end of their school days in a small town in the west of Ireland to their undergraduate years at Trinity College.
Rooney has adapted it with Alice Birch into a 12-part BBC Three series starring Cold Feet actress Daisy Edgar-Jones, 21, and newcomer Paul Mescal, 24.
She said: “The biggest challenge of adapting the book was trying to make the inner lives of the characters legible through their outward actions.
“In some ways Normal People is a novel about the differences between the characters’ outer and inner selves, so we had to find new ways to dramatise those differences on screen.
“As with all aspects of the adaptation, my co-writer Alice Birch was enormously helpful in tackling that challenge.”
Rooney said that she was always clear that she wanted the series to to be set and filmed in Ireland, in accordance with the book, and said: “I think that was important to all of us from the beginning.
“The book is set in a small fictional town in County Sligo, and in a few specific locations in Dublin, and none of us really felt that those places were generic or interchangeable
“We were committed to getting the environment right and doing justice to the specific setting of the story, and I think that’s become an important part of the show.”
Rooney said she was also involved in the casting process but tried to keep an open mind about the kind of actors who could fill the roles.
She said: “I was involved in the casting process from the beginning, but I was conscious that I didn’t want my pre-conceived ideas about the characters to overwhelm my judgment about who was best for the part.
“We found Paul quite early in the process and I think there was an immediate consensus that he was going to be our Connell.
“Then we had to look for a little bit longer to find Daisy. But as soon as they were on screen together, I think we all knew it was the right match.”
Normal People will be available as a boxset on BBC iPlayer from April 26.