On Saturday, Gillian – who played former prime minister Margaret Thatcher in the most recent season of The Crown – posted a photo of herself and Olivia enjoying a spot of lunch while in full costume.
“Happy birthday Queenie,” she wrote, alongside a picture showing Olivia caught mid-mouthful, with a jacket draped over her Queen Elizabeth II costume.
The new photo comes just days after Gillian commented on a clip that showed herself and the rest of the cast performing a dance routine to Lizzo’s Good As Hell, again in full costume.
Introducing the footage during an interview with US talk show host Seth Meyers, the former X Files star said: “Olivia apparently does a dance class in the area that she lives with a bunch of friends, on a regular basis.
“And the last time she did the dance, they had danced to that Lizzo song, and she asked if we would happen to be interested in maybe doing it, and she would video it? And then she would just share it only with her friends, the other dancers. So it was never meant to see the light of day.”
It wasn’t just snacking and busting moves that the cast used to pass the time though, with Olivia previously admitting that she got most of her co-stars hooked on Naked Attraction.
“We were given our own log cabins, but I don’t like being on my own,” Olivia explained. “So I forced Marion [Bailey, who plays the Queen Mother] to let me live with her. And she’s just too polite to say no.
“And once I said to her, ‘you’ve got to watch this, it’s brilliant, you see everybody’s willies and fannies and it’s really funny’... and she looked slightly horrified. And I said, ‘well what do you do of an evening normally, Marion?’, and she said, ‘well sometimes we listen to classical music and talk about plays’. Shit, I really brought it down a notch.”
Olivia did then claim that her on-screen mum “ended up loving it”, though.
All four series of The Crown are now available to watch on Netflix.