series in a recurring role in seven episodes, acting as a companion in six of them, but became a regular in this series, having had his "fingers crossed" that this would happen. Alex Kingston returned as River Song. Although Kingston did not expect to return before the fifth series, Moffat always intended for River to return to the series. James Corden also reprised his role as Craig Owens from "The Lodger" in "Closing Time", and Simon Callow briefly reprised his role as Charles Dickens from the first series episode "The Unquiet Dead", as did Ian McNeice who briefly reprised his role as Winston Churchill from the fifth series episode "Victory of the Daleks". A young version of Amy was played by Gillan's eleven-year-old cousin, Caitlin Blackwood, in the episodes "Let's Kill Hitler" and "The God Complex". Gillan and Blackwood first met on the set of the fifth series, but, although Blackwood had to audition, Gillan recommended her for the role. "A Christmas Carol" guest-starred Michael Gambon and Katherine Jenkins as Kazran Sardick and Abigail respectively. Guest stars of the main series included Michael Sheen (voice) as "House" in "The Doctor's Wife", Imelda Staunton (voice) as "Interface" in "The Girl Who Waited", Suranne Jones as Idris in "The Doctor's Wife", David Walliams as Gibbis in "The God Complex", Hugh Bonneville and Lily Cole as Henry Avery and the "Siren" respectively in "The Curse of the Black Spot", Mark Sheppard as Canton in "The Impossible Astronaut" and "Day of the Moon", and Daniel Mays as Alex in "Night Terrors". Production Development The sixth series was commissioned in March 2010, before the fifth series aired. Neither Peter Bennett nor Tracie Simpson returned as producers, with Sanne Wohlenberg covering the role for "A Christmas Carol" and the first two episodes filmed for the main series ("The Doctor's Wife" and "Night Terrors"). Marcus Wilson produced every other episode except "Closing Time", where Denise Paul produces and Wilson is credited as "series producer". Production designer Edward Thomas was replaced by Michael Pickwoad. Lead writer and executive producer Steven Moffat stated that the purpose of the previous series was to "reassure" the audience that the show was the same, despite the many production changes. However, he wanted this series to be more of a "ghost train" and "worry" the audience. The series is much more serialised than previous ones; the arc-driven nature was inspired by positive reactions