Steven Moffat has admitted that episode 11 of Series 9 is proving to be one of his most challenging scripts to finish yet.

Speaking at last week’s BAFTA NY panel he said: “I’ve got a script where I’ve set myself a ludicrous challenge.

“When episode 11 comes up in the next series of Doctor Who, you’ll see just how ludicrous a challenge I’ve set myself. Dear god! I’m in a state of panic about it.

“Even now, sitting here I am thinking, when I get back tonight could I just try another way of doing it? Remaining calm and knowing that even though the director is joining next week you’re going to have to wait until it’s right.”