Doctor Who spoilers follow.
Doctor Who showrunner Chris Chibnall has opened up about the companion reunion scene in tonight's (October 23) special.
'The Power of the Doctor' was Jodie Whittaker's last outing as the Doctor, with the next Time Lord, Ncuti Gatwa, set to take over.
The scene saw several former companions reunite for a kind of therapy session including the likes of Bradley Walsh and Bonnie Langford, who played Graham O'Brien and Melanie Bush respectively.
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Also returning were Sophie Aldred and Janet Fielding, who reprised their roles as Ace and Tegan for the centenary special. Katy Manning (as Jo Jones) and William Russell (as Ian Chesterton) also made cameo appearances in the scene.
Chibnall opened up to Digital Spy and other press, revealing that he didn't tell anyone he was planning the scene, he just asked the actors.
"It was one of those things where I didn't tell anybody. I was just going to be doing it and I just put it in the script and sent the script off," he said.
"It was interesting watching it as well, as it's about as metaphysical as the show's ever been in a weird way in the landscape of the Doctor, but I just thought this was the moment where we could ask and they were all really keen.
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"We got incredible messages back, they were amazing on the day. It was emotional in an amazing way," he added.
Whittaker, who was present for the scene, said "it was so emotional" as these people "paved the way" for the rest of them.
She said: "It was amazing just because walking onto set with these people, this is their show and you are a tiny drop in the ocean of Doctor Who and for us, we've got to tread lightly, we've got to earn our places.
"So to be on set with people who have paved the way for us to be here is a really emotional thing."
Doctor Who airs on BBC One in the UK. In the US, the show airs on BBC America, with series 1-12 available on HBO Max. Classic Doctor Who streams exclusively on BritBox in the UK.