WHEN a play calls for two actors to play cops with questionable parentage, how they decide who plays the bigger b******?

Former River City star Andy Clark and Gary: Tank Commander’s Robbie Jack are set to star in Broadway hit play, A Steady Rain.

It’s a story of two Chicago cops, Joey and Denny whose close friendship is tested to the limit when they make a decision that proves to be entirely wrong.

And the pair have more flaws than a three year-old’s argument for eating the last chocolate biscuit.

Joey is single and has a drink problem we learn in the play, written by Keith Huff of House of Cards and Madmen fame. He is also secretly in love with Denny’s wife.

Denny, we learn, is a part-time racist who cheats on his wife with prostitutes.

So who got to play Denny, the baddest bad boy?

“I’m Denny,” says Andy, who played nice Doctor Brodie in the BBC soap, holding up his hand in acknowledgement.

“We didn’t choose who we would play,” he says, grinning. “It was just sort of assumed. But it’s a brilliant piece of writing.”

Robbie, who played Jacko in Gary: Tank Commander agrees; “I’ve worked with Andy quite a few times, and I felt it didn’t matter either way. Both of the characters have so much about them.

The actor who grew up in Lossiemouth adds; “These guys, we learn both tried to become detectives a number of times, but failed. They’re trying really hard to stay on top of things and to help each other, but a series of events pulls it all down.”

The characters are written in varying shades of black and grey.

Andy reveals; “They’re both second generation ethnic minorities, Denny Italian and Joey Irish, and they feel they’ve been victimised.

“Denny is also very unorthodox in his ways, very old fashioned whereas Joey is trying to keep up with the times.”

What the play (described by the Chicago Tribune as "a gritty, rich, thick, poetic and entirely gripping noir tale") reveals is how quickly someone’s life can unravel.

It seems the old aphorism that we are all three steps away from being in a perilous state; lose the job, the relationship, the home . . . has some truth.

“It really does,” says Andy. “I was home at the weekend and I passed this guy with getting out of a car. He had a walking stick and his face was all battered and had terrible skin. He looked about sixty.

“It turned out to be a guy we all idolised when we were younger. The coolest guy in Blairgowrie.

“He didn’t recognise me, but I just thought ‘There but for the grace of God.’ You can never tell how you will end up.”

Robbie agrees; “In this play Joey is trying to keep Denny moving forward, showing him how to be a good cop, to keep him away from problems in the job, getting him to go to anti-racism seminars. And Denny is kicking against this.

“Yet, he’s being supportive of Joey when it comes to personal issues. He’s saying to him he has to get a missus. Joey’s personal life is falling apart.

“These guys are in fact holding each other up.”

Andy and Robbie are clearly on the same page in terms of understanding the script, working in harmony. But it’s no surprise. The actors have appeared on stage together in the past, in Tam O’ Shanter and in panto, in Perth two years ago.

Indeed, Andy was once Robbie’s mum.

“As is so often the case,” says Andy, laughing.

Robbie is delighted to be working with Andy for their first time alone on stage together.

Andy agrees. Sort of. “When I read the script I hoped somebody like Robbie would get the part.”

Robbie’s eyebrows raise and he laughs; “Somebody LIKE Robbie. Not necessarily Robbie?”

“Well, I meant I hoped to see Robbie in the role,” says Andy backpeddling for Scotland, and laughing. “But if not, somebody like him.”

The American accents will be no problem.

“I’ve done a few American accents over the years,” says Andy. “I think mine has gotten better over the years. Southern is my default.”

Robbie has also revealed a very convincing American, in plays such as The Crucible.

“The Chicago accent however is a little more difficult than New York,” he says.

“But we’ve been listening to YouTube clips of actor Dennis Franz from Hill Street Blues. His accent is authentic. And I think we will keep each other right.”

Both actors have more stage work coming up. Robbie will appear in the theatre version of Gary: Tank Commander at the Hydro.

“It is terrifying,” he says, grinning of appearing to 8,000 people a night. “But it will allow for massive acting.”

Andy goes back to panto this year in Dunfermline, playing The Demon King.

Meantime, they are set to play two desperate cops, trying to hold it all together.

How much does this parallel with the lives of actors?

“It’s totally the same,” says Andy laughing.

“No different at all,” agree his partner in stage crime.

• A Steady Rain, The Tron Theatre, September 16-24.