'Harry Potter' director says if Robin Williams had been able to play Lupin, he would've had a completely 'different interpretation' of the role

• Chris Columbus said Robin Williams would have been "brilliant" as Remus Lupin.
• Williams was interested in a few "Harry Potter" roles but the producers only cast British actors.

"Harry Potter" director Chris Columbus thinks Robin Williams would have had a different interpretation of the character of Remus Lupin if the late actor had been cast, though he'd undoubtedly have have "been brilliant" in the role.

Janet Hirshenson, who cast "Harry Potter and the Sorcerer's Stone," the first film in the franchise, told Huffington Post in 2016 that the popular movie series had a very important casting rule - all of the actors had to be British.

Although Hirshenson said at the time that Williams wanted to play Hagrid but was turned down because of the "British only" rule, Columbus said in a separate conversation with Total Film in October that Williams was also interested in playing Lupin.

"I had a conversation with Robin Williams, who wanted to play Lupin," Columbus told the publication. "It was very difficult for me to say 'It's all British. There's nothing I can do.'"

In a recent conversation with Insider, Columbus, who directed the first two "Harry Potter" films and produced the third, opened up about the franchise's decision to only cast British actors and how Williams would have done with the character of Lupin had he been cast.

"Robin would have been brilliant. It would have been a different interpretation - I thought David Thewlis was great - but Robin would have been brilliant," Columbus said.

He added: "Jo Rowling and myself said to each other when we first met, 'Look, we want this cast to be 100% British.' And by the way, I stuck to that."

Lupin is introduced in the third book and movie, "Harry Potter and the Prisoner of Azkaban," as the new Defence Against the Dark Arts teacher before Harry finds out that his new professor used to be best friends with his parents, James and Lily.

Williams spoke out about missing out on starring in the "Harry Potter" films in an interview with the New York Post in 2001, saying that "there were a couple of parts I would have wanted to play."

"Maybe one day. Say if [Harry] goes to Yale and becomes president," he added, joking about his potential future prospects with the franchise if it had crossed the pond to America.

Columbus told Insider that he was so strict about only casting British actors in all the major roles, his daughter Eleanor Columbus - who, like her dad, is American - had no dialogue when she played a minor character, Susan Bones, in the films.

Bones is memorable for being one of the first Hogwarts students in Harry's class to step up to the sorting hat in "Harry Potter and the Sorcerer's Stone."

"She worked about 80 days," Columbus said about his daughter's role. "But she never spoke because you know the rule was if you're not British, you can't speak."