The BBC have now confirmed that the British Tony Award-winning actress, Lindsay Duncan, will be starring in the second Doctor Who special of 2009. The BBC Press Office released a press release about the casting of the actress, and you can read that below;

Acclaimed actress, Lindsay Duncan will guest star in the second Doctor Who Special of 2009 on BBC One.

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.

Lindsay commented: "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."

Lindsay joins David Tennant as he continues his role as The Doctor in the second instalment of the four Doctor Who Specials to be screened throughout 2009, which 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."

The second episode is written by Russell T Davies and Phil Ford.

It is due to go into production in Spring 2009 and will be screened on BBC One later this year.

The Producer is Nikki Wilson; Executive Producers are Julie Gardner and Russell T Davies.

Doctor Who is produced by BBC Wales and is filmed in Cardiff.

The title of the second Doctor Who special of 2009 is currently unknown, but I will post it as soon it becomes available. The second special will air later this year on BBC One.