As "Doctor Who" prepares to celebrate its 50th anniversary in 2013, the BBC has revealed that Matt Smith and and Jenna-Louise Coleman (the upcoming companion) will be getting a visit from another iconic of British television. Dame Diana Rigg, who played Emma Peel on "The Avengers," will be guest starring in an episode next year alongside her real-life daughter, Rachael Stirling.

As always when it comes to "Who," details are being kept to a minimum, but Rigg and Stirling will play a mother and daughter on-screen and their characters are said to share a "dark secret." Described as "funny and original" by Stirling, the script for the episode arrives from Mark Gatiss who, in addition to appearing as an actor in two episodes, wrote "The Unquiet Dead," "The Idiot's Lantern," "Victory of the Daleks" and "Night Terrors."

The seventh season of modern "Doctor Who" will begin this fall and is slated to the feature the final episodes with Karen Gillian and Arthur Darvill as Amy and Rory with Coleman said to debut in the 2012 Christmas special.

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