Sally Rooney knew immediately that Daisy Edgar-Jones and Paul Mescal were the perfect "match" for the roles of Marianne and Connell in 'Normal People'.
The acclaimed author's hit tome has been turned into a TV series, which will air on BBC One and BBC Three, and the writer has admitted the team behind the show couldn't have made a better casting decision for the complicated on/off lovers.
Sally said: "Yes, I was involved in the casting process from the beginning, but I was conscious that I didn't want my preconceived ideas about the characters to overwhelm my judgement 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."
Sally, 29, also admitted that Marianne and Connell felt like "projections" of herself when she was writing the book, however, working on the show - which she also executive produced - allowed her to be "more detached" from the characters and she ended up feeling "sorry for them" for the first time.
Asked if seeing them on screen changed her view of them, she said: "I think it probably helped me to feel a little bit more detached from the characters, in a productive way.
"While I was writing the novel, I was completely alone with Marianne and Connell, and they really felt at times like projections of myself.
"Writing the show was a different experience, and it allowed me to see the characters in a new way, as if from the outside. I found myself feeling sorry for them - which I don't think I ever did when I was writing the book.