Broadchurch writer Chris Chibnall is set to replace Moffat as showrunner for the next full series in 2018, but neither writer had originally planned to write this year's festive episode.
"There was one big glitch, which was Christmas," Moffat told Digital Spy. "I was going to leave at the end of series 10 – I had my finale planned and what I wanted to do with it. I had a good notion of that.
"Then I learned at a drinks event somewhere that Chris didn't want to start with a Christmas, so at that point they were going to skip Christmas. There'd be no Christmas special and we would've lost that slot."
Moffat suggested that, if Doctor Who had skipped Christmas in 2017, it might never have got its much-coveted December 25 slot back.
"Doctor Who would've lost that slot if we hadn't [done a special] because Christmas Day is now so rammed. So I said, probably four glasses of red wine in, 'I'll do Christmas!' and then had to persuade Peter [Capaldi] that's how we were leaving.
"Then I had to work out how you could get mortally injured in one episode and spend an hour regenerating on Christmas Day, which I hopefully have done!"
But while a changeover of showrunners is an epic event for fans, Moffat further admitted that handing the reins over to Chibnall is "incredibly prosaic" in many ways.
"It's like handing over any job," he insisted. "Though Chris was incredibly, and is incredibly, fastidious about not wanting to seem to lurk behind me, ready to knife me in the back!
Chris Chibnall
"I never felt that – he was absolutely welcome to be there any time he wanted, I had no problem with it all. He's a good friend."
Thanks to The Moff, Doctor Who will return to BBC One this Christmas with 'Twice Upon a Time', in which our current Doctor (Capaldi) goes on one last adventure, teaming up with his very first incarnation (David Bradley).
Via Digital Spy by Morgan Jeffery
