In must-see episodes of the Channel 4 soap airing next week, Diane is left disgusted and furious when she finally discovers how badly Sinead (Stephanie Davis) has treated Esther over the past few months.
As the dust settles, however, Diane has some shocking advice for Sinead as she instructs her to stay out of trouble by pinning all the blame on fellow bully Ruby Button…
Digital Spy recently caught up with Alex Fletcher, who plays Diane, to hear her thoughts on the latest twists and turns in the Esther plot.
How do you feel about Diane being brought into the bullying storyline?
"I feel so lucky at the minute, because the Hollyoaks ratings have been the highest they've been in the last two years with this storyline, and to be part of that is just brilliant. Everyone's working hard and we've got our new producer Bryan [Kirkwood], who's just been absolutely fantastic.
"The bullying is such a big subject and it's been really interesting to see how all the different characters have reacted to it - and now you'll see how Diane deals with it."
The situation starts to kick off when a guilty Ruby comes to the O'Connor house and tries to reveal all about the bullying. How does Diane react?
"Ruby is very distressed when she comes round to the house, and she owns up to the fact that her and Sinead were the bullies. But Diane's reaction is, 'Do you know what? You're going to have to get out my house - I'm not having you spreading lies about my daughter!'
"Diane kicks Ruby out of the house and into the rain, and Ruby is in such a state that she ends up getting run over by Jack in his car. Then that's another web that Diane is caught up in!"
What happens next?
"Diane decides to look through Sinead's laptop and that's when she sees evidence that Sinead was one of the bullies. She then gives Sinead the opportunity to tell her the truth, but Sinead still doesn't admit it.
"It all kicks off as Diane gets Sinead's laptop, smashes it up and slaps her around the face! She asks Sinead how could she do this - how could she treat another human being in that way? Diane orders Sinead to bring Ruby back round, as she wants to have it out with the two of them. But Sinead explains that Ruby is in hospital after just being run over, so it's just a big massive knock-on effect."
What was the slapping scene like to film?
"It was a funny one, because we did a scene when I first started where Stephanie had to hit me. Both of them are quite volatile characters and I think that's where the bullying comes from. Diane has got that aggressive side in her and she uses her hands to express herself, which is not right. Diane is almost bullying Sinead herself by the way she reacts.
"We did have contact when we filmed the slapping scene - we didn't go for a fake slap. It was the same when we did it a couple of years ago, and it's better because you just get a more natural reaction. It didn't require too many takes, so Steph was okay and she survived! I felt awful, though, and I was hugging her between takes!"
In the end, Diane makes a shocking decision about how to deal with the bullying situation… What can you tell us about that?
"Diane decides that they should just cover up Sinead's involvement and pin the blame on Ruby. That's really awful to play because you think, 'Would someone really do that?' But I think some mums definitely would to save their own kids' skins.
"Diane is also going for a promotion at the college and she's got the opportunity to be Head of Student Welfare, so everyone's position is compromised. Diane also tells Sinead, 'If you admit you're a bully, you've got no future for you and your little baby'.
"Diane doesn't mention herself in those discussions with Sinead, but she's definitely thinking of her own position too. Bearing in mind that she's a one-parent family, she's probably thinking of her job quite a bit. So she just brushes it under the carpet, which is awful. It's a really strong week and I don't think Diane and Sinead are going to be the most popular!"
As a mum yourself, how do you feel about Diane's decision?
"In real life, I wouldn't cover up for anybody - I'm too honest! I wouldn't want to bring my family up to behave in that way at all, so if Sinead was my daughter, I'd expose her. There's no way that I'd cover up for anyone.
"But it was really, really interesting to play something completely opposite to the way I'd behave in real life. When I was saying the lines, I realised that some people really would react this way in the real world, but that's what made it brilliant.
"I think Sinead is a carbon copy of Diane in many ways, and she gets all of her bullying traits from her, as Diane is quite a tough cookie. She decides to bury this bullying problem, and I think Diane has got a few other things buried in the closet, to be honest with you.
"The viewers seem to be quite fond of Diane, but now I think they'll see a completely different side of her!"
You must be proud of the work that Steph has done on the storyline.
"Absolutely - she's one of the best actresses that I've ever worked with. She doesn't realise how good she is, that's what's so natural about her. Steph doesn't have to try, she's just got it naturally and she's fab. I do have to put her in her place now and then, especially when she's better than me in a scene! (Laughs.) But she's wicked."
On a separate note, a lot of viewers were expecting a Diane and Liam romance last year! Do you think they would have been a good match?
"I think Liam was just a bit of eye candy for Diane, and she realised it was nice to have a little attraction to someone. But I think they had more of a brother and sister relationship. We did a kiss under the mistletoe at Christmas and Liam said it was like kissing his sister, so Diane really had no chance there! But Liam is gorgeous and James who plays him is a really nice lad too."
How do you feel about the Hollyoaks fans always asking for more Diane scenes?
"Honestly, I can't tell you how much I appreciate that. I think really that's what's kept me in the programme - just the fact that people do say, 'We want to see more Diane'. It's brilliant to see that feedback. It's not always healthy to believe your own press, but it's really nice and reassuring.
"I think Diane is a good character, and with the way that the show is going now, it is very much storyline-based and it's all about the families. The scripts are just absolutely brilliant at the minute and Hollyoaks is well on its way to going in a new direction. Everyone's buzzing, and I am really grateful for the people who do show their support."
The O'Connor clan joined as a foursome but only two remain! Do you miss the rest of your on-screen family?
"Of course I do. When we found out they were going for a while, it was sad because we all came into the show together. But then again, I think it's nice to have that single mum and daughter situation. That's the reality of life and there's a lot of single parents out there.
"Although I do like that, it's not to say that the rest of the family won't make a comeback. It may not be just the two of us forever, but I can't say any more than that!"
Do Diane, Martha and Myra have any more scenes on the way?
"Oh yeah, I loved the scenes we did together and the viewers really seemed to like them. I've got quite a bit coming up with Carli, who plays Martha.
"Like I say, the focus is not just on the kids anymore - it's a good mix of everybody and there's loads more stuff to come. I've got so many scripts at the moment that I can't carry my bag as it's so heavy! It's brilliant."
Whenever your name is mentioned, people remember Brookside's Jacqui Dixon. How do you feel about people still talking about her so many years on?
"It's brilliant - I really didn't realise she was so popular! I'm really proud of that as it was my whole upbringing and I played that character for 15 years. It's nice now to get a bit of Diane recognition too, but Jacqui was brilliant and she's a tough one to beat. I'm doing my best to get Diane at that level, but I'm only two and a half years in!"
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Hollyoaks airs weeknights at 6.30pm on Channel 4, with first look screenings at 7pm on E4. Get the Inside Soap magazine on your iPhone or iPad