Script editor Matt Fitton said: “With these 60th anniversary stories, it was great to work out what the shopping list of characters would be, who we’d throw into the mix, how they’d bounce off each other and who would work well together.

“We felt it would be really fun to put Lady Christina and Jackie together. They’re at two different ends of the social spectrum and so having them run into each other would make for an interesting mix. We’re also doing our best to represent lots of different eras of Doctor Who. And with this particular setting, we’ve got an older Harry Sullivan turning up as well.

“We’re bringing together people we’ve worked with quite a lot over the years. We know they’re fun and enjoy recording, so it’s a great group of people - both characters and actors.”

Producer David Richardson said: “This episode is a glorious collision of much-loved characters. It's chalk meets cheese in the Once and Future universe, and there’s so much fun to be had...”

Colin Baker agreed: “I marvel at the fact that Big Finish can continue to produce such a high standard of script. Lisa McMullin has done a lovely job.”

Michelle Ryan added: “I love that I got to work with Colin. He's great. He's got that wisdom in his voice. I love the new dynamic (working with his Doctor), it's a totally different dimension that I didn't anticipate.”

And Camille Coduri said: “How brilliant - you've got your working-class girl (Jackie Tyler) and your aristo (Lady Christina). Jackie's relationship with the Doctor is love/hate, but they're more like sisters.”

Colin Baker