Sophie Aldred explains how her new Doctor Who book will resolve Ace's mysterious fate

Speaking to RadioTimes.com, Aldred revealed that she was approached about turning her hand to writing by BBC Books following the success of Doctor Who: Scratchman, penned by Tom Baker and published in January of last year.

Working with writers Stephen Cole and Mike Tucker, she developed the story for At Childhood's End, which expands on Ace's present as first touched on in Doctor Who spin-off The Sarah Jane Adventures.

"The root of it, obviously, is the tiny mention that Russell T Davies gave in The Sarah Jane Adventures all those years ago," Aldred explained. "Sarah Jane mentions somebody called Dorothy who’s running A Charitable Earth. And it all came from there. So, it’s all Russell’s fault!"

The idea of Ace having left the Doctor to become a reclusive millionaire philanthropist was picked up on in a teaser specially-shot to promote the release of Doctor Who's 26th season on Blu-ray, with Aldred reprising her old role. At Childhood's End, though, will explore the specifics of what happened to tear Ace and the Doctor apart, as well as seeing her reunite with the Time Lord in their newest incarnation...

"Dorothy really has her heart broken by the Doctor, because he’s the one person who she could really rely on, and then it all started to go wrong in season 26, where he became quite manipulative, and then questions started to arise," Aldred explained.

"It’s almost like that moment in childhood, where you think your parents are just the best and that they can do no wrong. And then somewhere along the line, you see them being human. I know the Doctor’s not human, but, you know, she sees him being alien at some point. She thinks, 'Right, you are not really us. You are not really me.'

"It’s a fall from grace, isn’t it? I think Dorothy’s had that experience of: 'Right, this is not the person who I thought he was. This is a kind of alien in disguise as a person.'

"So that’s given rise to possibly a bit of cynicism. If you look back, Ace is a very moral character. She always wants to do the right thing. Right at the end of the first story where Ace is the assistant, Remembrance of the Daleks, Ace turns to the Doctor and she says, 'We did good, didn’t we?'.

"I think that sets up the tone for her future, in a way. She wants to do good, and she’s doing good as Dorothy in A Charitable Earth. But she’s got this heartbreak. She really loves the Doctor and, you know, there’s a sort of yearning. She’s not quite in the world of being human, and she’s lost the world of time and space travel. So I see her as quite melancholy."

In At Childhood's End, Dorothy/Ace is thrown together with the Doctor (as played by Jodie Whittaker) once more, investigating a mysterious satellite alongside new companions Ryan, Graham and Yaz and working to unravel a malevolent plot that will cost thousands of lives.

We won't spoil here if Dorothy and the Doctor are able to patch things up, though Aldred did hint that the book will reveal new details about their complicated relationship, as well as touch on the various different fates outlined for Ace in Doctor Who spin-off media.

"With Big Finish and the comics and the novelisations and all these things that have come since, and fan-fiction even, everybody has had their own idea of what happened to Ace," she said.

"I thought it’d be really good to explore how that could be, and, without giving it away, I hope we’ve done that.

"And then the other things was, the way Ace joined the Doctor as well. Although Ian Briggs, who wrote The Curse of Fenric, he did explain about this time storm, and that she was flown up to Iceworld, and things like that. But I’ve always wanted to go into it deeper.

"How, really, did she get there? What was that all about? What did happen between her and the Doctor? So it was a great chance to explore that."

It was was Doctor Who's cancellation in 1989 that meant Ace's fate was left up in the air, and though Aldred says she was "so sad" not to get "closure" on the character, she can now appreciate how it's allowed the character to live on...

"Now, there’s all these possibilities for her, which is great! So, absolutely, it was a blessing in disguise."

Doctor Who: At Childhood’s End by Sophie Aldred is published by BBC Books on 6^th February