Denise Welch reveals why French teacher Steph Haydock has returned to Waterloo Road (BBC1, Wednesday)…

Where has Steph been?
“It’s never really been explained, but she’s found love and gone off with her boyfriend, Oliver, played by John McArdle. But when she returns to the school it’s as if she’s always been there!”

Why has she returned?
“Steph’s discovered that Grantly’s wife, Fleur, has early onset Alzheimer’s and has returned to help him through this traumatic time. Steph’s normally a comic character so it’s been nice to come back for a dramatic storyline. And Grantly is not only my favourite character, but Philip Brown, who plays him, is also one of my best friends.”

Why does Grantly listen to her when he’s normally so stubborn?
“Steph gets Grantly. She may not be a very good teacher, but she does understand his old-school style. Although he doesn’t show it, he’s delighted to see her. He’s someone who would never ask for help and that’s why she steps in.”

Have you personally been affected by Alzheimer’s?
“It’s an important episode for me as quite a few of my friends have had parents with Alzheimer’s including Fiona Phillips, Beverley Callard and recently Colleen [Nolan] lost her mum to Alzheimer’s. It’s a cruel illness as it robs you of your memories. I hope people will learn something about how it affects carers and loved ones from this heartbreaking episode.”

Would you consider returning to the programme permanently?
“Not at the moment as I’ve done six series and there’s a fantastic new cast now. But I’d never say never! Like leaving Coronation Street, it felt like the natural time to go. I’m motivated by change and am happy to be working on other projects.”

Have you ever considered becoming a teacher?
“When I was 17 I thought I should teach drama, as it was the only thing I was good at. But my dad and drama teacher talked me into applying for drama school instead. Thankfully I did – I’d have made a terrible teacher!”

Can you speak French in real life?
“My French is rubbish – which is just as well when you’re playing a terrible French teacher!”

What have been the proudest moments of your career?
“I’m really proud of Waterloo Road as it manages to hit some very strong issues, but is also something that the whole family can watch together. Corrie is also something I’m very proud of. I was landlady of The Rovers Return! Following in the footsteps of so many great characters is something I’ll take to my grave.”