'Spencer': Watch Kristen Stewart's Princess Diana Talk Christmas Presents With William and Harry (Exclusive)

See ET's exclusive clip from the upcoming biopic, starring Kristen Stewart as the late Princess of Wales.

Spencer, the upcoming biopic that stars Kristen Stewart as the late Princess Diana, shows the embattled royal wrestling with motherhood, life in the spotlight and the end of her marriage to Prince Charles, capturing an imagined Christmas holiday with the royal family in 1991.

In ET's exclusive clip from the upcoming film, directed by Pablo Larraín, Stewart's Diana sits on the floor of a bedroom at the queen's lavish Sandringham Estate with her sons, 9-year-old Prince William (Jack Nielen) and 7-year-old Prince Harry (Freddie Spry), who have some questions about Christmas. Namely, why their family opens presents on Christmas Eve instead of on the holiday "like everybody else."

"You know at school, how you do tenses?" Diana asks her sons in response. "There's the past, the present and the future. Well here, there is only one tense. There is no future, and the past and the present are the same thing."

The young princes, however, have a less-philosophical idea.

"Daddy told Harry it's because Father Christmas does queens and kings the day before everybody else," William explains to his mother. "So that we get the best presents."

"Actually, that was my little fabrication," Diana admits. 

"I believe Mummy," Harry sweetly offers, though William adds, "Daddy did confirm it, though."

"Oh, if Daddy confirmed it, it must be true!" Diana snaps. See the full scene in the video above.

Stewart spoke with ET about embodying the late royal as a mother at the Spencer junket last month.

"The whole thing about watching her, within that space when her children are close to her, it's a nucleus. It's a three-headed animal, sort of an unstoppable beast," she noted. "You don't want to mess with moms, you just don't do that."

"I think [Diana] feels so embodied and so unconditionally herself when she is with her kids," she added. "In all of the research, that I was like, 'Man, that is what we are protecting here.'"

Despite not personally having experience with motherhood, Stewart said she related to Diana on other levels.

"I mean, I'm a kid of a parent," she said. “I do know what it feels like, that exchange. I can’t say with certainty that I know what it feels like to be a mother. But I have, you know, I have all the natural feelings. I am human.” 

See more in the video below. Spencer is in theaters nationwide on Friday, Nov. 5.