Sam Stafford said: "It’s a real pinch-me moment when you get to go, 'I'm the companion of the Doctor!' I'm standing on the shoulders of giants. And it brings a different dynamic to be one of the few male companions - it's described in the script as a Laurel and Hardy sort of situation.

"Alfie is a happy-go-lucky chap. He's been travelling with the Doctor for a while and is very much enjoying his time. What I love about Alfie is that he’s a really kind guy. He deeply cares about everyone that he meets and wants the best for them. But he also loves a fight. He's quite a muscular man, so he brings an air of physicality that I’m not necessarily used to - fighting on audio is quite physical, despite it just being voice!

"We fight alien armies, but it does all boil down to that element of family, and the Doctor and Alfie and Chase build their own little family as well - it's really lovely, that dynamic works really well."

Natalie Gumede added: "When we first meet Chase, she is very dissatisfied with her life. She is a gaffer, a crew member in movies and TV, and she’s been unemployed for some time. So, she now works in a call centre and really is frustrated with going in and out, wondering when her adventures are going to start again.

"What I love about Chase is that she's so smart, quick-witted, and funny, and everybody around her enjoys that and plays off that. We also start to learn about her moral compass and how strong that is, especially against the majority. When the majority choose one direction, Chase listens to her heart and is willing to speak up."

And producer David Richardson said: "Natalie and Sam have been on my radar to play companions for quite some time. They're both very experienced in audio, bring bucketloads of enthusiasm to the recordings, and throw so much energy and vitality into their performances. So here they are: Chase and Alfie. The Doctor's new best friends - and soon to be ours too..."

Script editor Matt Fitton said: "The Eighth Doctor's had such a rich and varied life. It felt fitting that what we would do to celebrate it was invent a whole new era and bring in Chase and Alfie as new companions.

"We threw Natalie and Sam's names into the mix quite early on in the process, and so we were able to build those characters around them. This new team has a different energy and a different way of looking at the Doctor, and that brings out new things for Paul to do as well."

On kicking off this new era, the first episode's writer Alan Ronald said: "I was given a bit of a blank slate to introduce two companions. With Alfie, we hit the ground running, and he's already gadding about with the Doctor, and then we meet Chase, and see how the Doctor crashes into her humdrum daily life.

"Given that it arrives on the thirtieth anniversary of the Eighth Doctor first appearing, we had to find a way to touch on that, but not have it be all about that. I didn’t want it to be a look backwards, it had to look forwards. So, my approach to that was through Chase and the call centre, with her connecting with the Doctor across that entire period. We have a thirty-year period of storytelling condensed into her week!"

Natalie Gumede and Sam Stafford © Tony Whitmore