Steven Moffat teases next series of 'Who'

Doctor Who showrunner Steven Moffat has revealed that the next series of the show will continue the 'silence' arc from series 5.

Viewers heard a mysterious sinister voice announce that "silence will fall" in the final episodes of the most recent series.

Moffat told Doctor Who Confidential that the secret behind the voice will be revealed in the next series.

"What is that, who is that, who are the silence, what's coming?" he teased. "The whole point of the silence is next series.

"Also, River Song... who is she really? That's what we're going to find out next year."

Alex Kingston first appeared as the mysterious time-traveller River Song in the fourth series of the programme, in the Moffat-written 'Silence in the Library / Forest of the Dead'.

The sixth series of Doctor Who will air on BBC One in 2011.