'Who' director: 'The kids will freak'

Doctor Who director Richard Clark has hinted that an upcoming episode of the show will terrify children.

Clark previously confirmed that he would helm two instalments for the next series.

He wrote on his Twitter feed: "I'm scared filming this [episode]. The kids are gonna freak."

Clark later added that he was preparing to wrap production on his two-episode stint.

He continued: "Big finale today. Complex. Lots to co-ordinate. But it's looking seriously gorgeous."

He also praised the performance of star Matt Smith, but refused to confirm the identities of any guest actors.

"Matt's performance [is] a joy," he said. "Wonderfully talented actor. Sadly [I] can't reveal anything about guests, except that I'm delighted."

It was previously reported that actors Daniel Mays, Emma Cunniffe and Jamie Oram have been cast in the new series.