JK Rowling’s longstanding casting rule broken by John Lithgow in new Harry Potter series

Potterheads have been eagerly awaiting the arrival of the Harry Potter series, but they might not know about the behind-the-scenes 'rule-breaking' that came with its creation.

When it was announced in April 2023, fans of JK Rowling's wizarding franchise were instantly wondering who would be cast as their favourite characters.

Just as the original films, this series is based on the Harry Potter books, recasting Daniel Radcliffe, Emma Watson and Rupert Grint’s Harry Potter, Hermione Granger and Ron Weasley.

According to HBO, it's set to 'feature a new cast to lead a new generation of fandom, full of the fantastic detail and much-loved characters Harry Potter fans have loved for over 25 years'.

"Each season will bring Harry Potter and these incredible adventures to new audiences around the world, while the original, classic and cherished films will remain at the core of the franchise and available to watch globally," the network vowed.

A major rule was broken when the new celebrities were cast in the Harry Potter reboot (Warner Bros.)

While it's been confirmed that young stars Dominic McLaughlin, Arabella Stanton, and Alastair Stout will take on the roles of Harry, Hermione and Ron, respectively, there is one Hollywood icon that broke all the rules when he joined the Wizarding World.

It’s John Lithgow.

Known for his roles in How I Met Your Mother, Daddy’s Home 2, and Shrek, the 80-year-old is a TV and film icon.

However, he is famously American, which has always been a big no-no for Rowling when it came to the adaptations of her work.

Have you ever noticed that the cast of all eight Harry Potter films is overwhelmingly British?

Well, Chris Columbus, the director of Philosopher's Stone and Chamber of Secrets, opened up about the casting decision.

As per The Telegraph, he said: "Jo Rowling and myself said to each other when we first met, ‘Look, we want this cast to be 100 percent British’.

"And by the way, I stuck to that."

Having been confirmed as the next Albus Dumbledore, who was previously brought to life by Michael Gambon and Richard Harris, Lithgow is in for a ride.

John Lithgow is our new Dumbledore (Max Cisotti/Dave Benett/Getty Images)

The New York-born actor understands just how crazy of an opportunity it is, telling Screenrant: "It was not an easy decision because it's going to define me for the last chapter of my life, I'm afraid. But I'm very excited."

⁠According to someone involved in the original Harry Potter franchise, the great late Robin Williams was even turned down as a candidate for a role because he was American.

The original Harry Potter casting director, Janet Hirshenson, told Huffington Post: "The 'only British' rule was so important that Robin Williams was even turned down to play Hagrid… Robin had called [Columbus] because he really wanted to be in the movie.

"But it was a British-only edict, and once he said no to Robin, he wasn’t going to say yes to anybody else, that’s for sure. It couldn’t be."

So, why has the 'rule' changed now?

Who knows, but there’s actually been a few minor roles that have gone to people from the US. Verne Troyer provided the physical acting for Gringotts Bank goblin Griphook in Philosopher's Stone, though British star Warwick Davis voiced the character.

Meanwhile, Columbus' daughter Eleanor had a non-speaking cameo as Hufflepuff student Susan Bones.

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

According to reports, the Harry Potter series is set to release in 2027.