Secret still out there, says Russell T Davies.

Have you solved the mystery of Bad Wolf, the cryptic hidden message spread across this season of Doctor Who?

Well, no. You haven't. At least, not according to Executive Producer Russell T Davies, who has been keeping an eager eye on the various theories about who or what the Bad Wolf could be:

"Judging from the reactions I've had, a lot of people seem to think the Bad Wolf has already been revealed. Oh, it's the TV station. Oh, it's half a million Daleks. I've even got one friend claiming it's the Face of Boe! I must get better friends.

"I don't want to give anything away yet, but there is another revelation to come in Saturday's episode. We haven't discovered the true Bad Wolf yet."

UPDATE: The Bad Wolf was a message scattered through time by Rose after she absorbed the Vortex. It told her it wasn't too late to save the Daleks. She said: "I am the Bad Wolf. I create myself."