Despite her current status as one of the longest-serving companions in the show’s history, it always seemed as though Jenna Coleman’s time on ‘Doctor Who’ could end at any moment. Not only did rumors persist that she would make her exit in the wake of Matt Smith’s regeneration at the end of her first season, but she very nearly did leave at the end of the following season. If that’s news to you, go back and watch the end of ‘Last Christmas‘. That special essentially wrote her out before almost immediately writing her back in. That wasn’t an accident, as Coleman was in fact prepared to pack it in before deciding at the eleventh hour to stay on for one final season.

Coleman’s change of heart came so late in the process that then-showrunner Steven Moffat had already begun developing her would-be successor. As Moffat explained to the Radio Times:

“I vaguely had a set of thoughts about what the new companion should be like. There would have been elements in common [with Bill] – but your mind moves on in the interim. so maybe some of where we ended up with Bill has obscured what I was thinking about for Clara’s replacement, or the original version of Clara’s replacement, so I couldn’t really say now. Bill ended up being very much her own thing, I think. And very much Pearl Mackie.”

But the character was never quite fleshed out, as Moffat was never quite convinced that Coleman was ready to leave. Despite that, the special was very nearly ready to film before Clara’s fate was decided. Moffat continues:

“I didn’t feel as though we were quite finished with Jenna and Clara. And I wasn’t convinced, looking in Jenna’s eye, that was really ready to leave. And I don’t think anyone should leave ‘Doctor Who’ until they’re really ready to leave. So it wasn’t a massive surprise to me that she stayed. It was a bit of a surprise – I mean, we went to the Christmas read-through, ‘Last Christmas’, with her leaving at the end, and it was in the conversation after the read-through that she stayed. But you know, if you’ve got a star like that, you keep a star like that. Of course you do.”

This recalls a similar situation that preceded production of the show’s fourth modern season. At the time, Russell T. Davies found himself developing the Tenth Doctor’s new companion. The character – a journalist by the name of Penny – was largely scrapped when Catherine Tate expressed interest in returning to the show as Donna Noble. However, a version of Penny did appear as a minor character in the fourth season premiere ‘Partners in Crime’.

The first season of ‘Doctor Who’ following Moffat’s departure will air later this year, though the BBC has yet to announce a premiere date. Be sure to check back with for more ‘Doctor Who’ coverage as the premiere approaches.