Russell T Davies: The first Doctor Who Christmas special was "the greatest gift in British TV"

"I mean, it's very different in America, he said. "They don't show lots of big programmes on Christmas Day itself, do they? Here, on Christmas Day, those are the highest ratings of all, because those are when the big shows play. So it wasn't just a Christmas special, it was a guaranteed slot on Christmas Day itself, at 7.00pm, and that is literally the heart of the schedule for the entire year."

He continued: "It was like being given the greatest gift in British television you could possible ask for. So we had to raise the stakes! We had to deliver a great big blockbuster and entertain everyone!"

The special famously introduced Tennant to the role of The Doctor, in introduction that didn't happen until 40 minutes in.

"As a selling point for a Christmas special, it couldn't have been better," he said. "What a gift to put into my hands, come and meet the new Doctor! And David Tennant turned out to be one of the most successful Doctors of all time. So it was actually a great rush of energy."

The reaction to Tennant's introduction was everything they had hoped for: "It's like the finest audition piece in the world — not for David, he's already got the part, but it's like he's auditioning for the great British public, to say, "Come and like me." And I think it did! I think it worked! Aha!

Davies revealed they had no idea how the return of Doctor Who would be received and certainly hadn't planned on a Christmas special, which is why there had already been a Christmas story in the first season, which starred Christopher Eccleston.

"We brought back Doctor Who in 2005," he said. "I was so unaware of the possibility of a Christmas episode that I did a Christmas episode in our first series, where the Doctor meets Charles Dickens, and it's Christmas Day, and it's snowing, and there are ghosts. So that's actually secretly the first Christmas special, it just didn't go out at Christmas."

The first season was such a success "that the BBC turned around to me and said, 'Let's have a Christmas special'."

He added: "They ordered two more series and two more Christmas specials all in one breath. Which was wonderful, but I just saw my life disappear."

Will he be watching this year's special, Revolution of the Daleks, on BBC One on New Year's Day?

"Oh God, yes," he said, clearly still a fanboy. "I can't wait for this year. "It's the Daleks again, it's Jodie Whittaker. I am very excited. I can't wait!"

Check out what else is on with our TV Guide, or take a look at our new TV shows 2020 page to find out what's airing this autumn and beyond.