Chris Chibnall made casting the first female Doctor a “condition” of taking over as Doctor Who showrunner.

Executive Producer Matt Strevens revealed to Digital Spy: “Once Peter [Capaldi] had decided he was leaving, the next Doctor was always going to be a female Doctor. That’s what Chris wanted, that was part of his conditions of doing the job.”

He added: “We knew in our gut it was about time and it felt like the right decision, and the character is not gender-specific, in any way really. If ever there was a character that was never defined by gender, it’s the Doctor. The Doctor is gender fluid in that sense.”

Chibnall himself told the site: “It felt like a straightforward decision, it’s not that controversial. It’s very hard to think of many examples in its 55-year history where the Doctor takes a decision based upon gender.”