I'm getting annoyed now with all the criticism of current characters appearing in the 50th. We have to have people who are current and can make te story work, just having classic characters for te sake if it would detract from the story and make a mockery of it. If past characters can complement the story great, if not dont, and unfortunately due to age etc, a lot of them aren't feasible. Having Kate Stewart is fine by me, it's a nod to the past as she is the brigadiers daughter and she is the current head of UNIT (I think) ..