However, the casting agent for the production has claimed young British actors won't be able to audition because of Brexit.
Top casting agent Amy Hubbard tweeted that she’s seeking "a boy with a playing age of 9 to 12 years to believably play Prince William at 11 years old" in the film.
But she then clarified: "Must have a European passport (Not British European due to new Brexit rules from January 1st 2021)."
The post went on to say that the individual must be available from the end up January next year until March 30.
One Twitter user was quick to reply, asking: "Not British European? I’m pretty sure we can still travel?"
Hubbard replied: "It's not about travel. It's common on films that the passport for significant characters needs to match that of the financiers."
The film, directed by Pablo Larraín, will be set on The Queen’s Sandringham Estate in the 1990s when, over the course of three days, the Princess of Wales realised her marriage to Prince Charles was over.
Appearing on Jimmy Kimmel this week, 30-year-old Kristen was asked what it was like to step into the shoes of "one of the most beloved figures in the history of the world".
The US actress said that while she "didn’t grow up with her… the same way" as those who were adults when the Princess of Wales died, she did remember it as a child.
"It happened really quickly," she said. "I was really young, I didn't know what was going on."
Asked how she would approach the role, Kristen replied: "I mean, everyone's perspective is different and there's no way to get anything right.
"My movie takes place over three days, and it's this really poetic internal imagining of what that might have felt like rather than giving new information.
"We kind of don't have a mark to hit, we just also love her," she added.
There's a Princess Diana frenzy at the moment, at Netflix smash hit has introduced her in its fourth series, which launched earlier this month.
The role is being played by actress Emma Corrin, while Prince Charles is currently portrayed by Josh O'Connor, who also starred in season three.