'We had a lot of ideas in our bottom drawer, but it's getting empty now'
Promising viewers more twists and turns, Inside No.9 is set to shock and surprise when it returns to BBC Two for a third series this month. Creators Steve Pemberton and Reece Shearsmith tell Gemma Dunn how they manage to keep things fresh
Since it first aired three years ago, Inside No.9 has had viewers hooked, but even its creators - Steve Pemberton and Reece Shearsmith - are baffled as to how to define the BBC Two show.
"It's an anthology series..." offers Pemberton (49). "It's hard to define because some episodes will be more broadly comic and some will lean on the drama a lot more."
"As an experiment, we tried to write something that was completely 'BBC One' and it was fine - the notion of just writing a funny thing - but then it just feels like it's lacking something," chimes Shearsmith (47), before swiftly adding: "Not that it's easy to write something for BBC One."
"It was just surface comedy without something turning on its head," he elaborates. "It's not always giving it a twist, but something a bit deeper. You need something else."
That je ne sais quoi the formidable duo envisaged has materialised in an unrivalled mix of horror, thriller, drama and comedy. And it's a formula that's resulted in a third series of Inside No.9, with a fourth already confirmed.
"I think half-hour episodes is a really interesting format," explains Pemberton, who's appeared in Benidorm and Happy Valley.
"A lot of these kind of things would be stretched to an hour, but what we've learnt to do is tell quite punchy stories."
As with previous runs, the six single episodes (the first episode of series three aired as a Christmas special) are set in different, and seemingly innocuous, locations each week.
The only mainstay is that the action always occurs behind a No.9 door. But when the brief is so vast, where do you start once handed the keys?
"That is hard," notes Shearsmith, who created, wrote and starred in sketch show The League Of Gentlemen with Pemberton.
"We have a sort of creative platform where you can do anything, and parameters can sometimes help."
Yet there are key components. Aside from a feeling of claustrophobia, "they're often in real time and they barely ever leave the room or house that we set them in," he adds.
"And that's its own problem and challenge in a way - to try to keep the narrative moving on when you can't leave it and maybe the passage of time can help do that."
The actors - who've sustained a 20-year partnership - admit it gets trickier to conjure up fresh concepts.
"A lot of the ideas we've used we've had in the bottom draw for a while, and that bottom draw is getting a bit empty now," acknowledges Pemberton. "So it's harder but it's quite freeing.
"We never quite work out what is going to happen until the very end of creating an episode. We just start writing and halfway through say, 'This could happen now', or 'That could take this twist'. But yeah, it's hard changing it up every single week."
In the case of the upcoming restaurant episode, the duo was inspired after observing people squabbling over the bill at the end of a meal.
"But they were arguing about wanting to pay it, and we just came out and thought, 'Could that be one episode?'" adds Pemberton, who's from Blackburn. "And then it's about sustaining that one idea"
"By the end of the fourth series, we'll have written 24 pilots," notes Shearsmith, who hails from Hull.
"That's essentially what they are, one-offs. It's a prolific amount of ideas to try to keep being fresh about."
Past series have seen a host of famous faces appear, including Helen McCrory, Jack Whitehall and Jane Horrocks, and in this new run there are cameos from the likes of Felicity Kendal, Fiona Shaw, Jason Watkins, Philip Glenister and Keeley Hawes.
But while switching up guest stars certainly keeps things interesting, Shearsmith, a father-of-two, insists episodes aren't written with specific talent in mind.
"We don't even write thinking about ourselves in them, because we think that might hamper the best storytelling that might be available to us at that point," he reasons. "But then we say, 'Who will play that then?' and iron it out.
"It's also hard to put your eggs in one basket and hope for one person," he confides. "If you can't get them, you're forever feeling slightly disappointed."
While Shearsmith declares his love for writing and acting is a balancing act, he insists that he and Pemberton are far more interested in presenting the stories than vying for a starring role.
"We don't like to think of ourselves as the reason people watch it," he declares. "So it's just if there's a part for us in it, we'll do it."
And besides, the fun is in the writing.
"We're trying to do things that are surprising and it helps if you've got some secrets up your sleeves as the writers," explains Pemberton, who hints they've decided to lighten the tone for round four because series three is "quite dark".
"But they're all a joy and we love them," he finishes, beaming. "Long may it continue."
Inside No.9 returns to BBC Two on Tuesday, February 21 at 10pm