Dracula almost had an episode set in the 1970s

In other words, Dracula was very nearly That 70s Show.

“As I remember, the original plan was, really way back, we were going to do episode one as a very tight 90-minute version of the novel,” Gatiss told RadioTimes.com.

“Then we toyed with the idea of doing something in the '70s as a sort of bridging thing, because of our love of Dracula AD 1972.”

• How closely does Dracula follow the original novel?
• Dracula episode 1 almost doubles its audience in 7-day ratings

Starring Christopher Lee and Peter Cushing, the Hammer Horror classic brought the vampire to a (then) contemporary setting to prey on the descendants of his nemesis Van Helsing, and Gatiss and Moffat’s love of the film meant they were keen to reference it in some way.

“I mean, that was very early days,” Moffat said. “We knew because of the way Dracula is constructed as a story that each one would have to be different. You can't just have Castle Dracula again, and the terrified peasants again. You have to keep moving it on.

“So we kept trying to think of different things that had worked in the past. And of course there was the '70s update of Dracula in the Hammer movies which was great fun. So that was just one thing.”

“And then we sort of thought no, we can't run out of Bram Stoker so quickly,” Gatiss said.

Still, they kept the idea of bringing Dracula to a contemporary setting – and once they’d decided to drop the 1970s bridge, an idea emerged to have this as a cliffhanger ending.

“The third one was [always] going to be the present day,” Gatiss said. “And then it was just, a really straightforward idea of ‘Oh my God, what if we just do it as a twist?'.

“And it worked! It didn't get out.”

“It's tough these days to keep twists under wraps,” Moffat told us, “but slightly easier in Dracula because people weren't following us around. On Doctor Who and on Sherlock, people just follow you around."

Gatiss added: “We were filming in Whitby in modern clothes and nobody noticed, so thank God. It's actually one of those rare secrets that held right to the end."

Sadly, though, unless there actually is a second series we’ll never know what it would have been like to see Claes Bang cutting a rug as 1970s Dracula in flares and an afro. Time for the best fan artists to get cracking…

All episodes of Dracula are on BBC iPlayer