Jodie Whittaker and Mandip Gill on Doctor Who series 13 – and what it's like to leave the TARDIS behind

“It’s only now in the last week or so there’s been some tears shed,” adds Whittaker’s co-star Mandip Gill, who has played Yasmin “Yaz” Khan since 2018. “There is definitely something in the air now. We all realise that what we’ve been doing is coming to an end.”

Whittaker’s departure from Doctor Who was probably the worst-kept secret in showbusiness, with stories about her exit springing up months before she confirmed she was leaving, alongside showrunner Chris Chibnall.

“Chris and I always said we were going to do three series together, but then when you get to it, it’s a very different thing,” she says. “Sometimes it was like... ‘Are we sticking to this decision?’ There’s part of me that could absolutely say, ‘No, let’s keep going! Let’s go back on it!’ But to give the fans the level that they deserve, there has to be some sacrifice. You have to know when you’ve done it.”

Her departure is still a long way off, with three specials scheduled for 2022 following Whittaker’s third series in the TARDIS, which starts this week. Truncated due to COVID from 10 episodes to six, and featuring a mysterious catastrophe that sends the Doctor zipping across time and space, their new series is what we’re here to discuss. Hypothetical tears wiped away, Whittaker and Gill get to business.

“We haven’t been able to go to very many places, just Liverpool and parts of beautiful Wales,” Gill says. “So the sets have had to get bigger, the prosthetics are bigger, the monsters old and new... everything’s had to go to a new level. And I think naturally it does have to get to a massive climax.”

New monsters include creatures called the Ravagers and Karvanista, while some of the “old” baddies already confirmed to be back include the baked-potato-like Sontarans (whose rusty redesign Gill says is “so cute”) and fan-favourite, living statues the Weeping Angels. “They are genuinely terrifying, whether it’s being played by an actor or if it’s a statue – either one is creepy!” says Whittaker.

But monster redesigns aren’t the biggest change this year. Instead of a team of writers assembling a familiar mix of stand-alone episodes and two-parters, the entire six-part series, Flux – penned by Chibnall with returning writer Maxine Alderton co-writing episode four – is serialised, a creative decision forced by COVID but now embraced by cast and crew.

“Obviously for Doctor Who fans there’s been all versions over the years – there’s serialisation, there’s one-off episodes,” says Whittaker. “But in this, we’re ending episodes where literally the next beat will be a week later. We’re still going to different time periods and facing different monsters, but now there’s a bubbling over of the storylines, and it all builds like a slow pan on the hob.”

Guest actors include Line of Duty’s Craig Parkinson and Rochenda Sandall, The Inbetweeners’ Blake Harrison, Pirates of the Caribbean’s Kevin McNally and many more. But most significant of the fresh faces is new companion John Bishop, who encounters the Doctor and Yaz in the first episode and stays on board the TARDIS across the series.

“Mandip and I were so close to Tosin [Cole who played Ryan] and Brad [Bradley Walsh, who played Graham], but it’s been an amazing transition,” says Whittaker. “It’s just been a wonderful thing to end with, for me, the same kind of love and friendship and family feeling.”

Whittaker and Gill finished the regeneration episode in mid-October, followed by a fancy-dress wrap party (Whittaker dressed as Spider-Man, Gill as Kim Kardashian). But already the future of Doctor Who seems secure, thanks to the biggest surprise twist in Who history – the return of Russell T Davies, who ushered the programme into the 21st century as showrunner from 2005 to 2010 and brought in in writers including Chris Chibnall. He takes back the reins from Chibnall for the series’ 60th anniversary in 2023.

“Everyone’s excited about Russell,” says Gill. “For me, it’s so exciting and a relief to know it’s going on in safe hands. But we still have a year of what we’re doing. There’s so much more before that even happens.”

Apparently, the casting of a new Doctor will be announced “in due course”, and Whittaker says that she has no idea who her successor will be. But could Yaz be back alongside this new Time Lord?

“Never say never,” says Gill – though later, it seems clear she’s expecting to hand in her TARDIS key alongside her co-star. “When I started, I didn’t realise how significant it was taking over from other people, but now it’s happening to me. You’re not part of it, in that you don’t know what’s happening. Who are the companions? What are they going to do? I’m going to watch it, be nosey and think, ‘How’s it different to ours?’."

As Whittaker prepares to hang up her Who costume for good, she’s starting to grapple with her legacy. “This job has been, and continues to be, just extraordinary. And the thing is, I know it doesn’t end at the end anyway.

"Because you’re always the Doctor. You’re always someone’s Doctor, and what a wonderful thing and what a thing to treasure for ever. Frankly, I can dine out on this for ever.”

Doctor Who: Flux airs on BBC One on Sundays. For more, check out our dedicated Sci-Fi page or our full TV Guide.