Although
Mark Gatiss has already appeared twice (Professor Lazarus in
The Lazarus Experiment and an uncredited voice in
Victory of the Daleks), the
Sherlock writer/actor is to make another appearance in
Doctor Who. This year's finale
The Wedding of River Song sees Gatiss star as Gantok (pictured here) and will play The Doctor in a tournament of "Live Chess" on Vegas 12.
Actor
Simon Callow also returns to the show for the finale, reprising his role as Charles Dickens; previously seen in the Series One story,
The Unquiet Dead (written by, wait for it, Mark Gatiss).
