Kristen Stewart is set to play the leading role of an iconic member of the British royal family, Princess Diana in the upcoming movie by Pablo Larrain titled "Spencer." The big announcement was made on Wednesday and has garnered mixed reactions from royal insiders and experts.

As revealed by the director Pablo Larrain, the events of the movie will be stretched over a three-day weekend in the life of the late princess and her husband Prince Charles. This weekend happens to be one of her final Christmas holidays in the House of Windsor in their Sandringham estate in Norfolk when she decides that her marriage is not working out and she must carve a path of her own.

Now, royal insiders have given their reaction at the casting of the "Twilight" star in the role of one of the most famous women of the world. Stewart, who is an American actress, will start filming the movie in the year 2021.

Speaking with Fox, royal expert Leslie Carroll, author of "Diana and Charles: Royal Affairs and Notorious Royal Marriages" believes that if Stewart is able to "embody Diana's body language," her origin won't matter.

"Ms. Stewart has a built-in fan base from her 'Twilight' movies, so the producers may be counting on her name recognition to draw viewers. It might be interesting to learn whether she was auditioned for the role against other actresses and was deemed the best fit, or whether she was offered it," Carroll said. "If she can embody Diana's body language and convey her famous breathy, posh Sloane Ranger voice, it won't matter where she was born."

As per the publication, another royal expert Tom Quinn, the author of "Kensington Palace: An Intimate Memoir from Queen Mary to Meghan Markle" expressed his concerns about the "wrong accent."

Quinn is convinced that Stewart is a "great actor" who will probably manage to imitate Diana's mannerisms onscreen, but may draw criticism from the UK audience for "the wrong accent."

Neil Sean, author of "The A to Z of Harry and Meghan" said: "the news here in the U.K. is simply this... Why? There are many British actresses who would have been better for this role."

He goes on to explain that Diana's life story has been covered extensively previously. He believes until there isn't any "great groundbreaking new angle" in the movie there will not be anything for watchers to take away.

Sean is also concerned about Diana's sons Prince William and Prince Harry's thoughts about the movie. He believes they may "loathe any kind of exploitation of their late mother's name." As for his thoughts about Stewart playing the role, he feels her casting shows "out of tune the makers are with what the public's image and above all love for such a great lady is."

Produced by Larrain, the film includes script work by "Peaky Blinders'" scriptwriter Steven Knight. The behind-the-camera team will also include Fabula partner Juan de Dios, Jonas Dornbach, Janine Jackowski, and Paul Webster.

Kristen Stewart
Kristen Stewart attends ELLE's 24th Annual Women in Hollywood Celebration at Los Angeles at Beverly Hills on 16 October, 2017 Getty

"Diana is such a powerful icon, where millions and millions of people, not just women, but many people around the world felt empathy toward her in her life," Larrain told Deadline. "We decided to get into a story about identity, and around how a woman decides somehow, not to be the queen. She's a woman who, in the journey of the movie, decides and realises that she wants to be the woman she was before she met Charles," he added.