The BBC Doctor Who website have confirmed that Jemma Redgrave, who previously appeared in Doctor Who as Kate Stewart (Daughter of Brigadier Lethbridge-Stewart), will be reprising her role for the 50th Anniversary Special.
The BBC said:
"Jemma is part of a brilliant cast that is already known to include Matt Smith and Jenna-Louise Coleman who are joined by the returning David Tennant and Billie Piper plus screen legend John Hurt and Joanna Page. Filming is underway on the special which will be a 3D spectacular shown later this year."
In previous news, the BBC also confirmed Classic Series villains, The Zygons, would return for the anniversary special.
More casting announcements are expected shortly...
[Source: BBC Doctor Who website]