Jenna Coleman's cameo in Doctor Who's Christmas Day special was the final shot of showrunner Steven Moffat's reign, he has revealed.

The writer, who has stepped down after seven years at the helm of the sci-fi series, claimed the Victoria actress's busy schedule made it "complicated" to arrange her return as Clara Oswald.

He said: "I had to phone Jenna, who was incredibly busy on Victoria ... incredibly busy.

"It was a ridiculous schedule. She was well up for it but it was complicated to arrange."

"The very, very, very last thing I ever shot on Doctor Who was in fact Jenna's bit ... how many times have I killed that girl off and she was right there in my last shot," Moffat added.

"It's absolutely extraordinary."

The surprise cameo from Coleman is not her only Christmas Day TV appearance.