Cassie Plummer (Claire Sweeney) has left Coronation Street fans gobsmacked with her increasingly sinister behaviour towards show legend Ken Barlow (William Roache).

Over the past few months, she has been drugging his tea with antihistamines and stealing from his credit card.

In recent scenes, she was finally caught out by Ken, and confessed everything, before being thrown out and disowned by her loved ones.

Cassie’s drugging of Ken led the show stalwart to suffer a heart attack – though actress Claire Sweeney revealed that her alter ego never meant for things to go that far.

‘I do think she genuinely cares for Ken. I’ve said this before, it’s almost like a Pygmalion/My Fair Lady relationship with them. He teaches her things, he takes her to the opera, he teaches her about wine, they’ve been to Portugal together,’ she recalled.

‘They actually laugh together and they really, really care for each other. It’s just to keep him a little bit sleepy and then he needs her. There was one point after the holiday when he did say to her, “I’m quite able now, I don’t need you any more,” and she went into survival mode.

‘You’ve got to look at Cassie’s history. She’s had no one take care of her. She was a prostitute at one point, she’s been abused, her mum didn’t really want to know her. Her mum used to step in and save her at her worst moments with the drugs and stuff, she was there for her, but she’s pretty much a survivor. With Ken, it’s not just Ken it’s a lifestyle.

‘She doesn’t want to harm Ken, she doesn’t want to hurt Ken. Just keep him a bit sleepy and then he needs her.’

Despite how extreme this move was from Cassie, it was actually the petty theft that actress Claire struggled to get her head around.

‘I always think it’s a personality trait. She can’t help herself. She’s come from the streets and she can’t help herself.

‘A little Ninja here and there, a little air fryer, a little juicer here and there, “I’m going to get two and flog it and no one will know the difference.”

‘She was really smart with Tracy and the hair straighteners. She just can’t help herself.

‘That’s the bit I’ve struggled with, as Claire. Everything else I’ve come to terms with, the antihistamine and stuff because she genuinely loves Ken, adores him.

‘It’s that stealing bit, and it’s the petty stealing. If she was going to do it properly she’d do it big-time and clear him out and give him a bit stronger medicine, but it’s just the petty stuff.’

However, she did see one upside to Cassie’s sudden influx of money: ‘Suddenly she’s got the nails – as Claire I love the fact that she was allowed to have a French manicure and wear a bit of mascara. I was like, “Yes! Keep the antihistamine going!”‘