According to The Daily Record, Lindsay Duncan has been cast as the companion for the second Doctor Who 2009 special. Lindsay Duncan is a Scottish actress, best known for her roles in television dramas such as Rome and GBH. Apparently, Lindsay said:
"I'm thrilled to be involved in Doctor Who. I've never done anything like this before and I'm really looking forward to working with David Tennant and the Doctor Who team."
The paper also claim that Doctor Who lead writer, Russell T Davies, said:
"Lindsay is an incredibly talented actress and I've been an admirer of her work for some time. We are delighted to announce that she will be joining the team and playing the Doctor's most strong-minded companion yet."
The title of the second 2009 special which is written by Russell T Davies and Phillip Ford has not yet been revealed. The BBC have not yet confirmed this report but The Gallifrey Vortex will keep you updated on this subject.