The BBC has confirmed that acclaimed actress, Lindsay Duncan will guest star in the second Doctor Who special of 2009.
Lindsay is best known for her roles across stage and screen, including Shooting the Past and GBH and is soon to star as Margaret Thatcher in the highly anticipated BBC Two drama, Margaret.
In Doctor Who she will play Adelaide - the Doctor's cleverest and most strong-minded companion yet.
"I'm thrilled to be involved in Doctor Who," said Lindsay. "I've never done anything like this before and I'm really looking forward to working with David Tennant and the Doctor Who team."
Lindsay joins David Tennant as he continues his role as The Doctor in the second of four Doctor Who Specials to be screened throughout 2009. This will follow Planet of the Dead, due to air this Easter on BBC One.
Executive Producer and 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."
Due to go into production in Spring 2009, the second episode written by Russell T Davies and Phil Ford will be produced by Nikki Wilson and will be screened on BBC One later this year.