Doctor Who writer shares verdict on Billie Piper regeneration twist: “It’s the ultimate cliffhanger"

Doctor Who legend Mark Gatiss has given his verdict on the Billie Piper regeneration twist at the end of last season, describing it as the "ultimate cliffhanger".

The Reality War, which aired in May, saw Ncuti Gatwa exit the show, with the Time Lord regenerating into returning star Piper, who previously played companion Rose Tyler.

Speaking to RadioTimes.com at the Radio Times Covers Party 2026, Gatiss, who has written Doctor Who episodes including The Unquiet Dead, The Idiot's Lantern, The Crimson Horror and Robot of Sherwood, said: "Russell [T Davies] does chutzpah like no one else.

"I don't know much about what happened, if Ncuti Gatwa was going to do three years, but only did two - it was certainly a surprise that he was going, wasn't it? So I think if you have this sort of... it's like the ultimate cliffhanger, isn't it?

"It's like Sherlock in The Reichenbach Fall. It's like, well, this is a big one. And I mean, in a funny kind of way, it absolutely bookends the 2005 new show onwards - it's all about Billie! And then guess what?! So I haven't a clue. I know there's a Christmas special this year, isn't there? And after that, who knows?"

Also chatting to Radio Times, Alex Kingston, who played River Song in the BBC sci-fi gave her take on twist, saying she's "not buying" that Piper will be playing the next Doctor.

"I didn't see the Billie Piper twist coming at all. To be perfectly honest, I still don't quite believe it because she's not a Gallifreyan, she's a human," she pointed out.

"I think there's some playing going on here. But I don't buy that she's the next Doctor, and if she is, they're gonna have to work hard to convince me, because she's not a Gallifreyan!"

Notably, when she returned to the show, Piper was not listed as 'The Doctor' in the episode's credits - leading fans to believe, like Kingston, that there's more going on than meets the eye.

Speaking at the time of her return, Piper said: "It's no secret how much I love this show, and I have always said I would love to return to the Whoniverse as I have some of my best memories there, so to be given the opportunity to step back on that TARDIS one more time was just something I couldn't refuse, but who, how, why and when, you'll just have to wait and see".

Doctor Who will return to BBC One and BBC iPlayer this Christmas.

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