British actors have been told they cannot audition for the role of a young Prince William in a forthcoming film about Diana, Princess of Wales, due to new rules faced by the country post-Brexit.

A casting notification posted online calls for boys aged between nine and 12 to apply for the part of the prince, when he was aged 11, in the upcoming biopic, Spencer.

However, it says only European passport holders can apply and "NOT British-European due to new Brexit rules from 1st January 2021."

Amy Hubbard, the casting director on the film, later said in a post on Twitter that it was common practice for key roles in films to be filled with actors who share their citizenship with the project's financiers.

She said: "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, which stars Kristen Stewart as Diana and is directed by Pablo Larrain, follows the princess as she spends a weekend in Sandringham during which she realises her marriage to the Prince of Wales is coming to an end.

Speaking previously about playing Diana, Stewart told InStyle: "The accent is intimidating... because people know that voice, and it's so, so distinct and particular. I'm working on it now and already have my dialect coach.

"In terms of research, I've gotten through two and a half biographies, and I'm finishing all the material before I actually go make the movie."

Spencer is reportedly due to start shooting in Germany early next year.

A number of actresses have played Diana in the past, including in 2013 when Naomi Watts took up the role in a biopic titled Diana. Emma Corrin is currently starring as Diana in The Crown on Netflix. 

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