In the episode they will play a mother and daughter (rather apt) with a dark secret.
The episode will air on BBC One in 2013 and is directed by Saul Metzstein. Filming begins this week (2 July) at Roath Lock Studios in Cardiff.
Dame Diana Rigg, who will play a Yorkshire local, said: “The first time Rachie and I will be working together is on an episode of Doctor Who specially written for us by Mark Gatiss. How lucky is that?”
Rachael Stirling added: “What joy. I am looking forward to the madness of Doctor Who enormously. Mark Gatiss has written a gift of a script and an on-screen relationship between Ma and I that is truly delicious. We have never before worked together because the offers have not been tempting, but when such a funny and original script comes through you know the time has come.”
Steven Moffat is clearly excited: “Dame Diana Rigg, Rachael Stirling and a Mark Gatiss script – a combination of talents you could only get in Doctor Who ! Frankly, I'm terrified already!"
Rachel Stirlinghas appeared in Tipping the Velvet , The Young Victoria , Boy Meets Girl and last year's Women in Love.
Doctor Who News is reporting that the episode is provisionally titled “The Crimson Horror” and will the fourth episode in the second block.