I'm thinking about Donna, Martha, Rose, Jack, Sara Jane and Mickey as a team, and the tagline: "ONE OF THEM WILL DIE!' I'd watch that! Trouble is, I don't want to kill any of them. Rose Tyler was never created to die. None of them was. They were all created to show off Doctor Who's central premise: the world and the universe is wonderful, ordinary people can do great things, and the human race survives.
Did I ever tell you that Zadie Smith once wrote me to say that Bob & Rose is her favourite drama ever, and she watches an episode once a week -- and this was years after its original transmission -- in the hope that she'll create a character as real as Rose someday? Zadie Smith!!.
-- Russell T Davies, The Writer's Tale, pp. 100-101.