Jenna Coleman has insisted that she will not reveal whether or not she is leaving Doctor Who.
The actress, currently on screen with new Time Lord Peter Capaldi, is rumoured to be quitting her role as companion Clara in the sci-fi show.
But she told Radio Times magazine: "There's lots of rumours. We've sat down with [showrunner] Steven Moffat and we've all decided we don't want anybody to know which way it's going.
"If you know I'm in the next series - or if you know I'm off - you'll know how the story ends."
Asked about the Christmas episode, she added: "Because there's a surprise we've got coming, it's much better that nobody knows which way it's going to go - so that's where we're trying to keep it at the moment... that's all I should probably say."
But she added of her character: "It all becomes rather chaotic, as you can imagine, and that doesn't work at all - it becomes quite impossible."
Capaldi recently insisted that he was "not looking for a new assistant".
"I don't know where these rumours have started," he said. "What I can say is she is absolutely fabulous.
"She's been called upon to do things that I don't think any other companion has had to do, to show a kind of emotional range and I think she's done it absolutely brilliantly."
