Regarding Billie Piper in The Day of the Doctor Steven stated:
“I thought the story of Rose, which was beautiful, was done. I didn’t want to add to it, I didn’t feel qualified to add to it. That was always Russell’s [T Davies] story. The way Russell ended it in The End of Time was perfect. I didn’t want to stick another bit in. It would be wrong.
But we did want Billie Piper, one of the absolute heroes of Doctor Who, back in the show without interfering in the story of Rose Tyler. I think I might of spoiled something if I had done that.  Billie represents the rival of Doctor Who, more than anyone else. It’s all about Billie, it’s her show for two years. It’s really startling watching The Runaway Bride and you’re going, ‘Where is she? Where is she? Where is the star of the show?’

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