Speaking to Entertainment Weekly, she said, that she didn't know that she would play an important role in Series 6 of Doctor Who:
"When I first did Doctor Who with David Tennant, I wasn't expecting that at all," she admitted. "As far as I was concerned, it was just a two-episode story arc with me being held forever in a computer, or whatever. But Steven always intended that she would come back."
The actress also revealed that her favourite aspect of portraying the professor, whose identity is shrouded in ambiguity, is that the various incarnations of The Doctor never meet River in chronological order.
"The really exciting journey for me, and for Steven, is backtracking. The characters keep missing each other," Kingston added. "She's like The Time Traveller's Wife. In this particular season, and certainly in the first two episodes, what you see is her knowing that she's on the brink of the moment where the Doctor doesn't know any more who she is. And I think that's just tragic, really."
[Source: Digital Spy]
