Summary
Doctor Whoshowrunner Russell T Davies explains how Varada Sethu was cast in season 15 as a new companion, comparing her situation to a previous casting. Sethu surprised viewers by making an early debut in the third episode of season 14, “Boom,” where she played Anglican Marine Mundy Flynn. While Sethu’sDoctor Whoseason 15 castingwas confirmed before Ncuti Gatwa’s debut season aired, it has already been confirmed that she will portray an all-new character alongside the Fifteenth Doctor (Gatwa) and Ruby Sunday (Millie Gibson).
Davies has revealed toSFX Magazine(viaRadioTimes) how the production of “Boom” led to Sethu joining the cast of season 15. Directly comparing her casting to fellow companion actor Freema Agyeman’s brief appearance in season 2’s two-part finale, Davies revealed that Sethu’s early impression made her a favorite to join season 15. Check out Davies' recollection below:
I think we might as well just be simple with this, because we’ve already said she’s not coming back as Mundy Flynn. It’s one of those very simple situations, like with Freema [Agyeman, who appeared in Army Of Ghosts before being cast as Martha Jones]: when you cast a great actor, you need a new companion.
I was watching, like, the 15th edit of Boom, loving her. Every time I watch her, I think, ‘God, she’s brilliant.’ I literally think she’s brilliant. I used to watch her thinking, ‘God, what a shame we can’t work with her again.’ “I was thinking, ‘Should we go back to the 51st century, could we meet her again?’ and then I suddenly went, ‘Oh, let’s just cast her again. We’ve done that before. Lovely.’ The relief that went around the entire production and the BBC, everyone went, ‘Oh, great.’ It was the most instant ‘yes’ you’ve ever seen.
So, she didn’t even have to audition. We then invited her to come in for a meeting, but she thought she was coming in to audition [laughs] and it was the other way round. It’s like we were auditioning. We were wanting her to like us so much that she’d want to come back! We had a great meeting. She was kind of amazed and delighted. Lovely. Good stuff ahead. Completely new character, again, a completely new story, and that’s a great new story that will run across eight episodes.
How Has Doctor Who Explained Past Stars In New Roles?
While a familial connection could explain Sethu’s season 15 character, Davies’s tease suggests a larger story is at play.
Sethu isn’t thefirst mainDoctor Whocast memberto have taken on multiple roles, as Pete Purves, Colin Baker, Eve Myles, Agyeman, Peter Capaldi, and Karen Gillan had each played minor roles before joining as either the Doctor or a key companion. While Purves, Baker, and Gillan never had their pastDoctor Whoappearances tied into their more well-known roles, the other three actors each had reasons for their resemblance tied into the narrative. With Sethu, Davies is seemingly once more acknowledging her prior role in her companion’s upcoming story.
10 Doctor Who Theories About How Varada Sethu Returns In Season 15
After the shocking early debut of Varada Sethu in the Doctor Who episode “Boom,” many are eager to discover how what her role will be in season 15.
For both Agyeman and Myles, their originalDoctor Whoappearances were later explained by familial connections. Agyeman’s Torchwood employee Adeola is revealed to be Martha’s cousin in the season 3 opener, while Myles' Victorian maid Gwyneth is later established as Gwen Cooper’s ancestor. Capaldi, on the other hand, has a more narratively significant reason. The Twelfth Doctor’s resemblance to Capaldi’s past guest role, Caecilius, is acknowledged as a subconscious reminder to the Doctor about his values. While a familial connection could explain Sethu’s season 15 character, Davies’s tease suggests a larger story is at play.
Regardless of how she may return inDoctor Who, Sethu’s season 14 appearance has already left viewers excited. Sethu’s chemistry with Gatwa and Gibson as Mundy charmed viewers in “Boom” and left them wanting more, but there is still plenty of intrigue surrounding how her character will fit into the TARDIS team’s dynamic. With Davies eager for viewers to see the star’s involvement, it is clear her companion will be a core element of season 15.
Doctor Whoseason 14 is available to stream on Disney+ and BBC iPlayer.
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Doctor Who: Released on July 07, 2025, this series follows the Doctor and their companion as they journey across time and space, encountering a range of extraordinary friends and adversaries, expanding the universe of the long-running British science fiction series.
