Until The Crown, Meg just had one school musical under her belt and worked as a Red Brick at Legoland in Windsor.
Ed had slightly more acting experience, having just graduated from drama college.
Both applied to an open casting call and it is their magical chemistry that landed them the gig.
“As soon as we put [Meg] with Ed it was a done deal,” the show casting director told The Sunday Times Style magazine.
But it turns out that this was a serendipitous twist of fate for the young actors.
“We met a table read-through, neither of us had been cast yet, but they needed two people to just fill in and read for Will and Kate,“ Meg tells WHO.
“We were just very lucky to be the ones chosen and we just immediately clicked. I was so excited, that was definitely the biggest day of my life and I think we were both in the same boat and had just been rooting for each other straight away."
It was a momentous occasion where Ed also felt the sparks flying.
“The energy made sense and we got cast so everyone in the room must have thought that too," he adds.
The 24-year-old actor takes on the role of Prince William as he returns to Eton following the death of his mother, Princess Diana, in 1997.
It also follows William's journey as he comes to grips with the attention of paparazzi and thousands of screaming girls lining the streets wherever he goes.
While having hordes of young ladies lining up to meet him might sound like any hot-blooded male adolescent's dream come true, Ed quickly discovered that wasn't the case when he came face to face with it during filming. Not to mention all the paparazzi who were crashing the set.
“I think you develop a level of understanding by doing so much research and experiencing some of these things,” Ed says.
“To have an understanding of what it does feel like to be screamed at and have that level of energy thrown at you, it’s very intense, but no one can ever understand what it was really like for William.”
Meg's resemblance to the future Princess of Wales is uncanny as she sashays down the runway in a risqué replica of the Charlotte Todd see-through skirt Kate wore as a dress at their university charity fashion show in 2022.
The weight on Meg's shoulder must be heavy as she takes on the highly coveted role.
Not only is she playing one of the world's best-known and most photographed women, Kate is someone who everyone seems to have an opinion about.
For Meg, this was made much easier because she was portraying the future royal at a time before she had a public role.
“Because there wasn’t as much I could really focus on the script,” explains Meg.
“But I think there were some things which were always very evident from Kate in those days like her self-assuredness and her easygoing nature, that I could work on to bring her to life."
The Windsors are notorious for keeping their cards close to their chest and not revealing too much of how they think and feel, except for Prince Harry in recent years that is.
Since the Duke of Sussex and his wife, Meghan Markle, stepped down from their roles as working royals, the pair have given a series of interviews and he has penned a memoir. Spare became crucial to Luther in preparing for his role.
“It was important as I was listening to the audiobook all the time while filing,” he reveals. “It helped a lot vocally with how to project myself as Harry, but the material in the book which happens after the series did become irrelevant.
With the final episodes hitting the screen, The Crown comes it's a much-anticipated close- for now. Ideas for sequels, including a season focusing on King Edward VII and Wallis Simpson are reported to have been discussed by creators.
But with so much more juicy material coming about in recent years, including the weddings of William to Kate and Harry to Meghan and the fallout from their feud, could our trio of young stars be back one day to resume their roles?
Series creator Peter Morgan has previously revealed that he tries to maintain a “20-year rule” between real events and adapting them for screen to allow for some "perspective".
With Meg now 21, and Ed, 24, this would put them roughly at the right age bracket to come back to play Will and Kate for their wedding in the next seven to ten years.
For Ed though, he wouldn't be so keen to return.
“I think I'm glad it's stopping now,” he says.
"Even though it’s been an incredible experience… The show has had a level of historical significance and I think [if it continued] it could turn into something else. But I’m so glad I got this part.”
Season 6 of The Crown is streaming on Netflix now