British actors Alex Kingston and Colin Salmon are set to star in the next series of Doctor Who.

Alex, best known for roles in ER and Moll Flanders, will star in a Steven Moffat-penned two-parter as River Song – a mysterious character who meets The Doctor on an expedition to uncover the secrets of an abandoned library.

She’s joined by James Bond regular Colin Salmon, who also stars in the two episodes.

Alex said: “I used to watch Doctor Who through the crack in the door. I was so terrified, but I couldn’t tear myself away. I loved it so much and I’m so delighted to be a part of the new series.”

Award-winning actress Catherine Tate is reprising her role as Donna, the runaway bride, and will star as The Doctor’s companion throughout the new series alongside David Tennant.

The first episode of the eagerly awaited new series will witness Donna tracking down The Doctor during an alien emergency in modern day London.

Further guest stars already confirmed to appear this time around include Sarah Lancashire, Felicity Kendal, Lesley Sharp, Georgia Moffett, Lindsey Coulson, Tim McInnerny, Peter Capaldi and Phil Davis.

The fourth series of Doctor Who is now in production and will hit BBC One in Spring 2008.