Doctor Who showrunner Steven Moffat is preparing to hand over the keys to the TARDIS after an "overwhelming" but "amazing" ride — but first, he has "some real belters" in store for fans of the cult show.

Moffat, the lead writer and executive producer known for his labyrinth plots with complex twists and reveals, is preparing to regenerate into Chris Chibnall, who wrote for Doctor Who spinoff Torchwood.

He said he has achieved everything he wanted to in his six series of Doctor Who.

"I've been in this job so long that I've done everything that I could think of twice, probably," Moffat told podcast The Doctor Is In.

Moffat said the BBC had basically given him free rein, and never said no to any of his ideas or stared over his shoulder — even though he always invited them to.

"They let you go with it and execute you if it doesn't work out. Fortunately I haven't been executed yet," he joked.

Whovian influences

Growing up, Moffat's main fictional influence, like most others who have worked alongside him over the years, was predictably Doctor Who.

"Even if I was too scared to watch it, I was fascinated by it," he said.

"It's a show that seems to encompass every other genre so it's your one stop genre-shop."

Doctor Who continues to be wildly popular in its 44th year. ( Twitter: @bbcdoctorwho )

He also cited other as major influences Star Trek and Star Wars, Narnia, the Hobbit and Dr Tom's Midnight Garden — which he admits "I've been consistently ripping off for decades now."

But it was the magical aspect of his favourite books and television shows that fascinated Moffat, rather than the science fiction side of things.

"I know that will make some people cross," he said.

"But Doctor Who has always been more like that, more the magical end of things — it's about the wizard and the magic flying box which looks like a phone box.

"It's got that feel to it, which is why I think it entrances children."

Feckless thrill seeker or demi-god?

Moffat said there is one aspect of Doctor Who's character that he continues to explore in his mind.

"I was always quite interested in the idea of, for all we know he's just a bumbling, attention-seeking, adrenaline junkie running around the universe, but he must appear to everyone else as an awesome god who sorts everything out," he said.

"Are there places where they worship him, does he have a reputation that's completely at variance with the feckless thrill seeker we know him to be? I still find that interesting.

"He's not really keeping the universe in order, except by default, but people think of him that way, understandably, and sometimes he plays up to the image and he's not really that at all. I've always found that quite interesting."

Peter Capaldi and Jenna Coleman, on tour in Australia in 2014. ( AAP: Nikki Short )

But how old is the Doctor? Is he really 900 years old, as once said?

"Because of all the time travelling in a time machine he does, there's no way he would know how old he is," Moffat said.

"You can't take entirely seriously anything the Doctor says. He's not in the business of telling the truth about anything, there's an endless stream of distraction coming at that man.

"If he hasn't told you his name why would he really tell you his age? And in any event, how could he possibly know what it is?

"I think he makes up an age that sounds cool."

The final TARDIS trip

Moffat said he would finish his tenure on a high note with "some real belters" that are coming up in his final series.

And as his diary entry for the last day of shooting looms, the man who has a self-described "pretty epic" workload and hasn't had a weekend off since 2009 is planning what he will do after the final wrap — "go on holiday".

David Tennant was the Doctor from 2005 to 2010. ( BBC )

This is a man whose wife has had to book a separate hotel room for him to work in while on family holidays.

Moffat is pragmatic about what will come after the holiday.

"I'm not short of offers and I'm not short of ideas," he said.

The new guy

He acknowledged that handing over to new showrunner, Broadchurch writer Chibnall, is not without emotion.

"I'm sure I'll feel very sad. Particularly when Chris's new version of the show goes out and the circus comes to town and I'm not in it anymore," Moffat said.

"I'm sure I'll have my moments of 'what have I done?'

"But that aside, it's good to have an exciting past to look back on, and it is time to get on with new things."

He said he wants Chibnall to have the best time ever with Doctor Who, and to be happy he was persuaded to do "the most difficult job in the world".

"He's just starting to realise what it's all like. He will have the best time and do an amazing job. It's overwhelming but it is amazing. It is amazing," he said.

Steven Moffatt spoke to Paul Verhoeven on The Doctor Is In podcast.