ACROSS a table in a Glasgow bar, Scot Squad stars Karen Bartke and Darren Connell are sharing stories about trolley boys, double-jointed elbows and treading comedy’s thin blue line.

The pair are back on our TV screens in BBC Scotland’s spoof fly-on-the-wall police documentary as po-faced desk sergeant Karen Ann Miller and her eternal tormentor man-child Bobby Muir.

With the show now in its third series, their double act as Officer Karen dealing with Bobby’s catalogue of hapless antics – think stunt kites, mobility scooters, dodgy CCTV, a stolen face and heroic banana-eating marathon – has become a fan favourite.

When we meet in the suitably law-themed setting of the former Sheriff Court building (now the swish Citation Taverne and Restaurant) the contrast to their comic alter egos couldn’t be starker.

Karen’s laid-back demeanour is the polar opposite to the stiff, buttoned-up persona of her namesake, while Darren’s off-duty style is light years away from Bobby’s ubiquitous Parka and psychedelic wolf emblazoned sweatshirts.

What does carry over, though, is the magic of their on-screen chemistry. They have a shared sense of humour and the knack of finishing each other’s sentences that is forged in strong friendship.

Some viewers, it seems, would love to see that develop into something more. Darren – blushing to the roots of his hair – recounts one such story which involved a taxi driver asking if the pair had been romantically intimate yet.

Karen roars with laughter as he blurts out the tale, not repeatable in a family newspaper. “When people start talking about whether we are going to get together, that is a bit weird,” she says.

Protective big sister perhaps best sums up her own relationship with Darren. Karen, 44, clearly dotes on her 29-year-old co-star who, unlike Scot Squad’s larger-than-life Bobby, is naturally shy and takes a bit longer to come out of his shell.

Any notions I had about how our interview may pan out are soon balled up and tossed in a corner.

Be it Karen showing off her party piece of having double-jointed elbows (they’re super bendy) to Darren revealing his ability to hum and whistle at the same time (uncanny and oddly mesmerising), they make for hilarious company.

Garrowhill-based Karen had dreamed of an acting career since her teens, but it wasn’t until 2010 that she finally took the leap of faith, leaving her job as a research and development manager for a company which sold property search reports to conveyancing solicitors.

“I joined Glasgow Schools Youth Theatre when I was 16. I considered applying to a drama college, but lost my nerve,” she says. “I bottled it and didn’t fill in the forms. I went to university, got a job afterwards, joined an amateur theatre company and was a hobby actor for a long time.

“Obviously being an actor is difficult because you don’t have a steady income, but I thought: ‘to hell with it, I’ll try it for six months and see how I get on.’”

Karen hasn’t looked back. She was spotted by Scot Squad creator Joe Hullait while performing at a comedy improvisation group and invited to audition for the Comedy Unit produced show.

Recent jobs include a five-month contract with the BBC Radio Drama Company in London which included roles in Watership Down, Stardust and Harry Hill’s new remote prison drama Life On Egg.

“It has been an incredible job and I’m gutted it’s over,” she says. “I would love to do more radio.”

Darren, who grew up in Springburn and now lives in Bishopbriggs, has grafted equally hard. “I’m not trained as an actor,” he says. “Everything is self-taught.”

Prior to landing his breakthrough role in Scot Squad, he spent almost a decade working as a supermarket trolley collector.

“I’m quite similar to Karen in that when I was younger I wanted to do drama but was too shy to pursue it,” he says.

“When I was working as a trolley boy at Asda I always dreamed of doing comedy. I studied television production because I thought that might help get me in. I tried to be an extra but I never got any jobs.

“My first big thing was a crime reconstruction about the Ice Cream Wars. I played a character called Fat Boy. They put a mattress down outside the STV studios and I had all these guys jumping on top of me. I lay there thinking: ‘At last, I’m an actor!’”

Away from Scot Squad, Darren is steadily building his reputation on the stand-up circuit. He will return to the Glasgow International Comedy Festival in March with his new show, Darren Connell: No Filter, and last week launched an eponymous podcast.

In her spare time, Karen sings in a classic rock ‘n’ roll covers band called The Sentinels. “We do the police hockey gig every year,” she says. “This year people wanted to get selfies for the first time. Last year, though, was when I became conscious that the police were really getting into the show.

“They seem to love it. I’ll tell you what, Scottish police officers have got observation skills second to none – they can spot you from a mile away. Other than a girl in Boots one time, no one else knows who I am or recognises me.”

Not even the cunning disguise of a fancy dress costume could fool one eagle-eyed cop. “Last Halloween I dressed up as a 16th-century washer woman ghost in a mob cap with my face painted black and white like a skeleton,” she says.

“I was sitting on the Fish Cross in Ayr when, from the other side of the street, this random guy – who it turned out was a policeman – shouts to me: ‘Excuse me, are you Officer Karen?’”

The duo would love to see Scot Squad return for a fourth series. “I’m so chuffed to be a part of it,” says Karen. “I watch it as a fan as much as anything. While a lot of humour lately has been quite biting and negative, I feel ultimately, at its core, our show has a wee bit of heart in it.”

Scot Squad is on BBC One, Wednesdays, 10.40pm