Joe Cornish had a massive task. He had to take the most overused legend in British history—King Arthur—and make it feel like something a ten-year-old in South London would actually care about in 2019. It wasn't just about the swords or the magic. It was about the faces. When you look back at The Kid Who Would Be King cast, you aren't just looking at a list of child actors; you’re looking at a masterclass in scouting. Most of these kids had never been on a film set. Now? They’re leading major franchises and prestige dramas.
It’s weird how some movies just evaporate from the public consciousness while their actors go on to run Hollywood. This movie is the poster child for that phenomenon. It didn’t break the box office. In fact, it was a bit of a financial heartbreak for 20th Century Fox. But if you watch it now, the chemistry is undeniable. It’s authentic. It’s messy. It’s exactly what a group of awkward teenagers trying to stop a medieval sorceress should look like.
The Breakout: Louis Ashbourne Serkis as Alex
Alex is the heart of the story. He's not a "chosen one" because he’s special; he’s a chosen one because he’s kind. Louis Ashbourne Serkis had a lot of pressure on him. Being the son of Andy Serkis—the literal king of performance capture—comes with baggage. People expect you to be a prodigy.
Honestly, he nailed it.
He didn't play Alex as a hero. He played him as a tired kid who was sick of seeing his best friend get bullied. There’s this specific scene where he pulls the sword from the stone in a construction site. It’s gray, it’s raining, and he looks terrified. That’s the nuance that makes the The Kid Who Would Be King cast stand out from typical Disney-fied adventures. Since then, Louis hasn't just rested on his laurels. He showed up in No Return and The Queen's Gambit, proving that his performance here wasn't a fluke. He has this grounded, soulful quality that’s rare in young actors.
The Dynamic of the Four
The movie works because the central quartet feels like a real group of outcasts. You have:
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- Bedders (Dean Chaumoo): The loyal, nerdy best friend. This was Dean’s first big role, and he provided the emotional stakes. If Bedders didn't believe in Alex, we wouldn't either.
- Lance (Tom Taylor): The bully-turned-knight. Taylor was already a bit of a veteran compared to the others, having appeared in The Dark Tower. He brought a necessary friction to the group.
- Kaye (Rhianna Dorris): The cynical one. Dorris is fantastic. She represents the audience’s skepticism. Her transition from a schoolyard antagonist to a knight of the round table provides the movie’s best character arc.
The Merlin Factor: Why Two Actors Were Better Than One
One of the smartest things Joe Cornish did was splitting Merlin into two versions. You have the "Young Merlin" played by Angus Imrie and the "Old Merlin" played by Sir Patrick Stewart.
Angus Imrie is the secret weapon of the The Kid Who Would Be King cast.
He is delightfully strange. He does this rhythmic, bird-like hand gesture thing to cast spells that honestly should have looked ridiculous. Instead, it’s iconic. Imrie, the son of Celia Imrie, has this theatrical energy that feels ancient and teenage at the same time. He’s wearing a Led Zeppelin t-shirt and eating fried chicken, but you totally believe he’s a thousand-year-old wizard.
Then you have Patrick Stewart.
Look, you don't hire Patrick Stewart unless you want gravitas. He doesn't have a huge amount of screen time, but he grounds the film. When he speaks about the soul of Britain being fractured, he’s not just talking about a fantasy plot. He’s talking about the real world. His presence gives the younger actors something to lean against. It elevates the movie from a "kids' flick" to a legitimate entry in the Arthurian canon.
Rebecca Ferguson and the Villain Problem
Villains in family movies are usually cardboard cutouts. Morgana could have been boring. But Rebecca Ferguson—fresh off Mission: Impossible and just before Dune—decided to play it with a terrifying, serpentine stillness.
She spent a lot of the movie encased in prosthetics or CGI vines. Most A-list actresses would hate that. Ferguson leaned into it. She understood that Morgana isn't just an evil witch; she’s a manifestation of the world’s bitterness. The contrast between her cold, calculating performance and the raw, unpolished energy of the kids creates a genuine sense of peril. You actually think she might kill these children. That’s a hard line to walk in a PG movie.
Why the Casting Matters for the Movie's Legacy
We need to talk about why this ensemble didn't lead to a $500 million box office haul. It wasn't the acting. The The Kid Who Would Be King cast delivered exactly what was asked. The problem was likely the marketing. People saw "another King Arthur movie" and checked out.
But watch it today.
The diversity of the cast isn't forced; it reflects what London actually looks like. It’s a multicultural "Round Table" that feels earned. When Alex recruits an army of school kids to fight undead knights, the screen is filled with a cross-section of modern Britain. It makes the legend feel like it belongs to everyone, not just the history books.
Career Trajectories Post-2019
If you're wondering where they are now, the list is impressive. Tom Taylor has moved into more mature roles, appearing in The Bay and Us. Rhianna Dorris has continued to work in British television, maintaining that sharp, screen-stealing presence she showed as Kaye. Angus Imrie is everywhere, from Fleabag (as Claire's creepy stepson) to voice work in major animations.
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They grew up.
That’s the beauty of catching a "cast of kids" at this specific moment. They are caught in amber at that awkward age where their voices are changing and they aren't quite sure how to move their limbs. It adds an accidental layer of "coming-of-age" realism to a movie about monsters and magic.
Practical Takeaways for Fans of the Film
If you’re revisiting the film or discovering it for the first time because you saw one of the actors in something else, here is how to appreciate the casting even more:
- Watch the background kids: Many of the "knights" in the final battle were local students. Their reactions to the CGI monsters (which weren't there during filming) are surprisingly great.
- Look for the chemistry: Notice how the physical height differences between the four leads are used for comedy and character development. Lance towers over the others, which reinforces his initial role as a bully.
- Pay attention to the "Merlin Hand Gestures": Angus Imrie reportedly practiced those for weeks to ensure they felt like a "language" rather than just random waving.
- Check out Joe Cornish’s other work: If you liked the "kids vs. the world" vibe, his earlier film Attack the Block is essential viewing (and features a very young John Boyega).
The legacy of The Kid Who Would Be King cast is one of untapped potential that eventually found its way. The movie might have been a "flop" by Hollywood's cold, hard numbers, but as a talent incubator, it was a massive success. It remains one of the most underrated ensembles of the last decade.
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To really dive deeper into this world, the best move is to watch the "Behind the Scenes" features on the physical release. Seeing the training camps where these kids learned to sword fight gives you a much deeper appreciation for the physical labor they put in. It wasn't just green screens; it was months of choreography and bonding that translated perfectly to the screen.
The story of King Arthur is about finding worthiness in the unexpected. This cast proved they were worthy of the mantle, even if the world took a few years to catch up and notice them.
Next Steps for Enthusiasts: 1. Track the Actors: Follow Louis Ashbourne Serkis and Angus Imrie on industry databases like IMDb to see their upcoming 2026 projects, as both have transitioned into significant character acting roles.
2. Comparative Viewing: Watch Attack the Block immediately after to see how Joe Cornish utilizes young, unknown talent to create high-stakes tension.
3. Research Arthurian Roots: Read the "Le Morte d'Arthur" sections regarding the Lady of the Lake to see how faithfully (and playfully) the cast interpreted those specific character beats in a modern setting.