Corrie's Steve is so determined to keep his depression diagnosis a secret, he even puts his relationship with Michelle on the line. Actors Simon Gregson and Kym Marsh tell Susan Griffin why they're so proud of the poignant storyline.

STEVE McDonald has been Coronation Street's affable goofball for so long that actor Simon Gregson admits he had reservations when he first found out his character was set to develop depression.

"I first found out a few months ago," recalls the 40-year-old. "Our amazing producer Stuart (Blackburn) called me to one side and let me know about it. My first thoughts were, ‘Hmm, have you chosen the right guy for the job?', because of the kind of comedy element and the silliness that Steve brings to the show."

But it wasn't long before Gregson realised it was a brilliant move. "If it could happen to Steve, it could happen to anybody," he says.

Poignantly, the scene in which Steve is told he has depression was shot on the day the news broke that Hollywood star Robin Williams has killed himself.

"It was a bit like, ‘Wow, crikey, Robin Williams'. He was an unbelievably funny man, a genius," says Gregson.

As audiences have seen, in recent weeks, Steve has been growing increasingly distant from his family and friends, and acting in an ever-more erratic manner, failing to show up for work and making rash decisions, including the purchase of a sports car and "a ridiculous Christmas" he's set to lay on for his daughter Amy.

But unlike viewers, his partner Michelle has no idea what's going on.

"She thinks he's an idiot, but he's her idiot. That's why she loves him, but she can't understand why he's changed so much. He a shadow of himself," explains actress Kym Marsh, who joined the soap as Michelle in 2006.

"She feels like he doesn't want to spend any time with her. He's not talking to her, and every time they get a minute together, he disappears. She thinks he doesn't love her any more."

Things are set to come to a head for the couple when she suggests they get away for the weekend - Steve's reluctant so Michelle gives him an ultimatum: tell her what's going on, or it's over.

Although his doctor's diagnosed the depression, Steve remains in denial. The actor, who celebrates 25 years in the soap next month, and is married to Emma with two children admits that he has suffered a little bit with depression in the past.

"There's no set way to play this role. Some people can have it and not know. Some people can have it and their friends and family don't know. We're also aware there has to be peaks and troughs, good days and bad days," he says.

Marsh, who came to prominence in the band Hear'Say, has also spoken of her struggle with depression. "I have friends who've gone through depression and still are," says the 38-year-old.

"I think it's something a lot of people will be able to relate to, whether you're the person going through the depression, or someone close to a person suffering. That's the beauty of the story really, it's touching on all subjects."

Despite attempts from Steve's mum Liz (Beverley Callard) to initiate a reconciliation, the pair won't be together at Christmas.

"Michelle's absolutely heartbroken, she's devastated," says Marsh. "She's lost the man she loves and she has no idea what she's done wrong. And he's not bothered, that's what kills her so much."

"He's in such a bad place, he can't even see what's happening in front of him," explains Gregson.

Neither of the actors are sure how the storyline will play out, but Marsh believes Steve will eventually open up about what's really going on.

"I think ultimately, that will be how they come back together," continues the mum-of-three (Marsh also had a fourth child, Archie, who tragically died at birth). "Michelle can be feisty but she's a very supportive character. She's the mother hen really and she enjoys looking after people. I think once he tells her, she'll absolutely be his rock, because that's what she's like."

Coronation Street, tonight, Wednesday and Friday