Katherine Parkinson and Will Sharpe join forces in Defending The Guilty - a brand new courtroom comedy that shines a light on an often messy and flawed legal system. Gemma Dunn hears more.

Courtroom dramas may be a mainstay on TV - but what happens when you add comedy into the mix?

Your Honour, please stand for Defending The Guilty. A brand-new BBC Two sitcom written by Cuckoo's Kieron Quirke and based on Alex McBride's book, Defending The Guilty: Truth And Lies In The Criminal Courtroom.

The six-part series follows idealistic young barrister, Will Packham (helmed by the brilliant Will Sharpe), as he's "shown" the ropes by his cynical, worldly-wise pupilmaster Caroline, played by Bafta winner Katherine Parkinson.

Will must not only navigate his way through a criminal justice system seemingly designed to be as confusing as possible, but he's also required to deal with his fellow pupils, each of them after the same job at the end of their training and more than happy to stab each other in the back to get it.

Can he succeed and hold on to his principles? Or will the system claim another victim?

"It certainly raises questions about the legal system and moral questions," Sharpe, 32, says of the show. "[My] character believes he is a good guy and he seems to be a good guy, but the series gradually puts that theory under strain."

"As Will knows, I really enjoyed playing somebody ostensibly with no redeeming qualities," chimes Parkinson, 41, with a laugh.

"Quite often I have played supposedly quite lovable characters and it turns out it comes quite easily to me to be utterly horrific.

"But I still think you feel sorry for her - and it's a good contrast with Will's idealism and youth," she concludes. "Caroline just operates in a very kind of 'legal' way."

So where does the comedy come in?

"Kieron really prioritises the plot," begins Parkinson, who's well accustomed to the genre, thanks to her coveted role as Jen Barber in The IT Crowd.

"But it's a really clever thing to wrap up a case in half an hour and make it funny and have an ensemble playing," she says.

"He makes that seem quite effortless, but it's doing a lot, and that's why I hope people will enjoy it.

"Some comedies lay out their stall, it's just going to make you laugh, but this is something that's supposed to be representing a world fairly accurately and hopefully asks questions as well as mainly being funny."

"What I liked about it was that Tom George, the director, has very good taste," offers Sharpe, who earned his humour stripes with such shows as the self-penned - and darkly comic - Flowers.

"He gave us boundaries within which to work and it meant that we could feel quite mischievous, which is a really good atmosphere for comedy.

"So I definitely felt like that was a nice dynamic between us and the show, as a whole, and the shoot," he adds.

"Sometimes it felt like we were just being naughty just by playing the scene."

As for getting into character, the distinctive court dress certainly helped the London duo.

"I loved the gowns," quips Parkinson. "I found it very useful because it gave you an immediate status. Running down the stairs with it flowing behind you, it really does give you a sense of misplaced self-importance."

"I weirdly felt like it's quite a funny outfit, it's quite ridiculous in a way," Sharpe testifies.

"I think I read that originally the theatre of court is designed to, in a superstitious way, intimidate defendants into taking the process seriously, so it was to give status to the procedure," he recalls.

"I guess even in a relatively small number of weeks you get used to it, it's just what you wear to work..."

"I mean the wigs are ridiculous and uncomfortable," Parkinson pitches in. "I just think some people look incredibly noble in a wig, and other people - me - just look really silly.

"What was the reason behind the wig?" she says, turning to her co-star.

"Did somebody say it was because all of them having the same wig somehow put them on an even...? I can't remember, but it is objectively absurd."

Costumes aside, the legal framework is simply there to service the characters and their stories, Sharpe determines.

"These are messy, human, flawed people in a messy, flawed system that was built by people, and that's what makes it funny, and that's what makes it interesting," he elaborates.

"These aren't superheroes, and this isn't as grand and austere a world as it might seem." he vows. "It's run by people who are failing constantly and trying to stay on top of everything."

"I have always been interested in [the law]," admits Parkinson. "I did have aspirations to go into that world because - we were saying - it's pure theatre really.

"I say 'I toyed' - I also toyed with being an astronaut and a cat too," she says, smiling.

"But I think the subject I chose to study at university [classics] was one where a lot of people went into diplomacy and law, but the idea of being a diplomat is so far-fetched to me," she concludes.

"I don't think it was ever realistically within my reach."

Are there parallels to be drawn between the courtroom and acting, then?

"When you go up for parts as an actor, generally speaking, you have no idea who you've gone up against - and that's deliberate," Parkinson muses.

"Whereas it must be very different if you're a barrister, competing openly.

"I got into [acting] to get away from competition," she follows. "It isn't competitive - particularly when you're doing theatre, for instance, you're doing something together.

"Sometimes I find the nature of filming can feel oddly competitive, but when it's comedy it never is because it's always about the comedy that happens between you.

"I know from the outside it can look as if acting's a competitive world," she realises.

"And I know actors that make it that, but they're generally in LA. It's not been my experience."

Is a second series of Defending The Guilty on the cards?

"I think Kieron has great ideas and it was a very good experience, so I think we'd all be up for it," Parkinson says tentatively.

"But you never really know with these things. I'd like to play Caroline again, definitely."

"The stories are just there to ask the questions, and then the audience becomes the jury, and so similarly to the lawyers in the story, as performers, we're just there to make a case," Sharpe finishes.

"What people make of that is not really up to us."

Defending The Guilty premieres on BBC Two on Tuesday, at 10pm.