Car Share's Sian Gibson: I thought I'd ruined Peter Kay's career

“Everyone knew that Peter would be the one who made it,” she gives a warm smile. “He was constantly making films. My mum has all these VHS at home of all the short films he made that I was in. He’d edit all of his meticulously while most people just banged it together.”

The two bonded over a shared love of comedy and a down-to-earth background. “I’m not from an acting family,” shrugs the 41-year-old. “Dad’s a builder and Mum didn’t work. If I was 20 now I probably couldn’t have afforded to go to university. And I always loved comedy so I was never going to be a serious actress.”

She did take things a little more seriously than Kay, however. “I played Electra in a very radical college version,” she recalls. “In the final scene, I was crying over my dead brother’s ashes with Adagio for Strings in the background. Peter had to come on as a messenger. Very serious. Every night, just before he walked off stage, he’d look at me, look at the audience, roll his eyes and walk out. Everyone was in hysterics. The director was going mental – me in floods of tears and he tuts and rolls his eyes.”

After she graduated, she worked as a jobbing actress while Kay’s star rose steadily – but they stayed in touch and he found her roles as Yvonne in That Peter Kay Thing, Young Mary in Phoenix Nights and half of wheelchair pop duo 2 Up 2 Down in Britain’s Got the Pop Factor… “Things were great at the beginning of my career. Because I’m short, I always played younger parts. I was in my 20s and always played teenagers. Then I hit 30 and that doesn’t work anymore. It all just dried up.”

She quit acting, got married, had a baby and started work in a call centre, but stayed in touch with Kay. She’d often go out with him and his schoolfriend Paul Coleman. So much so that Coleman – who wrote the initial Car Share script with Tim Reid – based Kayleigh on Gibson, which is partly why Kay sent her the script in the first place. “Kayleigh is the fun version of me,” she gives a big grin. “But she was a lot younger than me so I didn’t even think of playing her.” Then Gibson’s daughter Gracie, now five, needed a hip operation and was in a body cast, unable to move for weeks. Kay started popping over for advice on the script and before she knew it, she was helping him write the entire project. Gradually the roles evolved until John, the supermarket assistant manager, and Kayleigh, the promotions rep, were basically Peter and Sian with funny hair.

“It was a great release at a tough time for me; Gracie was on a beanbag just flat out in a cast. I enjoyed writing it, but I didn’t think beyond that. Even when we started filming I didn’t take it seriously. I was just turning up and having a laugh. For the first series, we didn’t even have caterers. Every day we’d all go to a Toby Carvery for lunch, except Friday when it was fish and chips. At the end of six weeks, I couldn’t fasten my blouse – I just wanted a salad or an apple.”

They filmed the show in 2013, it dropped on BBC iPlayer in 2015 and her life changed. “When I first saw it, I thought I was dreadful – I was worried that I had just ruined Peter Kay’s career.” No one else did. It became the most-watched show on iPlayer and then when it transferred to BBC1, it got over six million viewers.

“Even Peter was surprised at how everyone responded to it,” she smiles. “I was back working part-time – then it came out and straight away I got an agent and…” – she shakes her head – “it’s like I’ve got two different lives.”

In her new life, she’s the star of Murder on the Blackpool Express alongside an impressive lineup of big names – including Johnny Vegas, Griff Rhys Jones, Kevin Eldon, Mark Heap, Una Stubbs, Sheila Reid and Nigel Havers. She plays Gemma, who runs the Blackpool coach company that’s plagued by murdered passengers.

“When I went to that read-through I was starstruck – I couldn’t even look at Nigel Havers,” she giggles. “I was too scared to speak to him. I started talking posh whenever I was near him because I didn’t want him to think I’m common.”

As for Vegas, who plays despondent driver, Terry who has an unrequited crush on Gemma, “Peter told me… he’s great, you’ll get on great,” she says simply, which was all she needed to know. It’s not quite a case of hero worship but she’s clearly very fond of Kay. “He’s my model for success,” she nods. “I still find it really strange that he’s got all the hype because he’s just the same now as he’s always been. Obviously, he knows how famous he is – he doesn’t do Facebook and keeps himself very private, but when we hang out we do the same things we’ve always done. I listen to him a lot – he’s annoyingly right.”

Certainly, his career advice has done her no harm. She’s got an episode of Inside No 9 coming up and, she says with carefully controlled excitement, a part in the forthcoming League of Gentlemen reunion, reprising her small role of Trish: “Steve Pemberton played Pop, Mark Gatiss was his son Al and I was Al’s girlfriend who Pop was all over.” She’s clearly thrilled at the whole idea. “I’m going back in as the same character but we’re now married with children.”

She’s tried drama – an episode of Death in Paradise – but found it silly when she had to pretend a CGI stick was a real dead body. What she’d really like to do is work with Sharon Horgan – “I’d love to do a great women’s piece and she’s so good at that.”

Our chat is over and she’s getting ready to pick up her daughter from school. “I don’t feel like I need to go to every opening – and I’m uncomfortable with all of that,” she says, then gives a wicked grin. “I sound like I’m a wholesome family girl. I’m not. I’m not just sat at home reading stories and baking. I’m just doing whatever comes along and enjoying it. If the attention I’m getting now had happened ten or 15 years ago I might have been falling out of a club with Dean Gaffney – but now it’s different. I’ve grown up. I think."

Murder on the Blackpool Express begins Saturday 11th November at 9.30pm on Gold