Many award-winning actors have met Queen Elizabeth through the years, though only a handful can attest they've been invited to a royal sleepover at Windsor Castle.
Helena Bonham Carter, who plays Princess Margaret in season three of The Crown, is one of the privileged few, reports News.com.au.
"They actually call them sleepovers," nods Bonham Carter in a chat with news.com.au.
"I think The Queen has about 10 of them a year so she can meet certain people, and I have to say, when I stayed over, it was a really odd group. It was about six years ago when I was still with Tim [Burton, her director ex-husband]. Daniel Craig was there with Rachel [Weisz, his wife], and there were other people in the arts as well, and also, the Brazilian Ambassador.
"I stayed in the Prince Charles Suite. It was a thrill and you really felt like you were in The Crown. And I remember there was a lady standing by the door, and she just carried on standing there," she laughs.
"And we went to the toilet, came back, and all our bags had been unpacked automatically. I said to her, 'Are you all right?' and she said, 'I'll just be remaining here. Do you want your bath to be drawn? Will you be wanting tea in the morning?' It was amazing. It was really surreal," she says, shaking her head.
And what of her interaction with the Queen herself?
"Well, the Queen was in full regalia and she was wearing a tiara. We all had to dress up [for dinner] and I sat next to the Duke of Edinburgh, who was very mischievous.
"He took us on a full tour of Windsor. They have an amazing library there which is basically the history of England. And what I liked about them was that there was a feeling that they feel they're just borrowers, that they didn't see it as their property."
Did anything surprise Bonham Carter about Her Majesty?
"Well, when the Queen smiles, she lights up. It's so genuine, it really is."
Bonham Carter's interactions with the younger royals have been decidedly less formal.
"I met Harry and William on Mustique [island] years ago. I got very drunk and I had just given birth to my daughter, Nell, and I asked William to be her godfather.
"And he said, 'You don't want me to be the godfather,' and I said, 'Oh, honestly, my son, Billy has 11 godparents including Johnny Depp and we've used them all up. And now we have Nell and she doesn't have anyone,'" she recalls, laughing.
"We were all pretty jolly on that Mustique trip."
Olivia Colman, who plays Queen Elizabeth in this season of The Crown, had a more sobering experience with the royals. "Well, because of my job, I've been invited to things like attending a charity dinner that Prince William is patron of, and when you meet the Queen, you say, 'Hello, Your Royal Highness.' And I've been very lucky to meet and curtsy on a couple of occasions," Colman tells news.com.au.
And has she refined her curtsy over the years?
"I don't think so," she laughs, though Colman is famously modest to a fault.
"I think I was a bit rubbish at it, but they're very forgiving. No one has pointed and laughed at me."
Bonham Carter has met many of the royal family, past and present, over the course of her life, including Princess Margaret.
"I met her twice in my life because my uncle was a guard outside Windsor and he began a lifelong friendship with [Princess] Margaret. So I met her when I was little, which was very exciting, and then again at about 30, when she commented that I was getting better at acting.
"I said, 'Oh thank you,' though she was implying I'd been dreadful to start with," she chuckles.
"But now it's really funny that I'm playing her, and frankly, it was definitely in her interest that I did, in fact, get better at acting."
Having met Bonham Carter on the set of The Crown several months ago, I remind her of her revelations that she contacted Princess Margaret via a seance.
"Yes. She was bossy and told me that in order to play her, it was paramount that I got the smoking and the holder exactly right."
Her portrayal of the Queen's little sister has garnered some of the best reviews of Bonham Carter's already esteemed career.
Has Princess Margaret weighed in from beyond the grave?
"No, she hasn't come through," she laughs. "And I haven't contacted her."
She did however, get Princess Margaret's casting approval during that initial seance.
"Yes," she nods. "She said she was happy I got the role and not the other actress they were considering. This role was a true gift."