The debut of Ncuti Gatwa as Doctor Who's 15th Doctor and their new companion, Ruby Sunday, has already been welcomed positively from critics and fans following the series' 2023 Christmas special. Despite this reception and the 14th season set to premiere in May 2024, the show is already undergoing a cast shakeup with a new companion on the way for the 15th season.

It was reported on Friday that Millie Gibson, who made her Doctor Who debut in the 2023 special The Church on Ruby Road, will only serve as The 15th Doctor's companion for the upcoming season, according to The Daily Mirror. She will reportedly not be appearing in the 2024 Christmas special, either, and will be replaced in the following season by Varada Sethu.

The decision was reportedly made by showrunner Russell T. Davies.

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“Millie Gibson has all but left now and there’s a brand new companion, which is really exciting,” an unnamed insider told the Mirror. “Russell is keeping things moving and isn’t letting the grass grow, that’s for sure.”

Sethu's addition to the cast was said to be met with excitement from everyone working on Doctor Who. She is a veteran of film and TV, and is best known to wider audiences for her portrayal of the rebel Cinta Kaz on the Star Wars series Andor.

“Varada is a real gem, Russell was just blown away by her talent,” another reported insider told the Mirror “The cast and crew have really warmed to her and he’s sure the fans will too.”

While the BBC and production company Bad Wolf have not commented on the decision to replace Gibson, Gatwa took to social media to share their affection for Gibson and the pair's time on the show. Gatwa shared an image of the pair in costume with the phrase “My lil” alongside a heart and a Gemini astrological sign.

Season 14 of Doctor Who is scheduled to continue in May 2024.