It seems entirely uncharacteristic for Hermione Norris to be so unsettled.

After all, she is the queen of cool, whose collected demeanour and piercing stare have made her a household name in TV shows such as Wire In The Blood, Kingdom, Spooks and of course Cold Feet, her blonde bob and periwinkle blue eyes making a fool of anyone who crosses her.

And yet she is nervous about the simple prospect of appearing at the Oxford Literary Festival, because more than happy in character, she is less at home in her own skin.

“It’s a funny paradox,” she concedes shrugging, “because I’m fine in front of a camera being someone else, but as soon as the spotlight is turned on me, I’m rather uncomfortable. It is something I have always struggled with oddly,” the 51 year-old tells me.

Talking from the set of current BBC TV show Luther, Hermione is one of the headline acts at Oxford’s current lit fest.

But as it’s her friend, journalist, radio presenter and former BBC producer Matthew Stadlen, who will be interviewing her on The Sheldonian stage on Sunday, she said yes.

“I expect I will feel very self conscious because I’m quite a private person really, but I like Matthew enormously and I trust him,” she says firmly.

She is an inspired choice, her 30 year career proving high profile and consistent. Her cool, calm demeanour and crisp delivery meaning that her roles have been dominant and memorable.

“I am very fortunate,” she smiles. “I have played some very strong women and I feel like I have had the best of TV. I have loved the characters I have played – they have all been unapologetically strong women.”

Something none of her fans are remotely surprised at.

But it was her reprisal of Karen in Cold Feet last year, that created a whole new generation of fans.

And yet she was against the reunion when the idea was first suggested. “I wasn’t very keen. It was such a loved and successful TV series and I didn’t want to undo that, because it was risky bringing it back.

“And then it was received incredibly positively.”

So was it strange revisiting the coming of age story over a decade later? “Yes because it really made me take stock of where I was and who I was at that time. And I do have a degree of ownership over characters such as Karen because I played her three to four years on the trot, so I feel like a guardian of that. I was pleased with how she develops.”

And yet Hermione prefers to hide away in Somerset with her husband and two children, than play the fame game, emerging only to work. “I do wonder how my career would had gone if I had embraced all these things. But I am what I am, and who I am.”

Happy as Larry in the countryside, she has thrown herself into motherhood, enjoying the tranquility away from London.

“It’s so much more pastoral here in Somerset and we have a very quiet, straightforward life.”

Has that meant making sacrifices then? “Having children has changed me. Absolutely. You make big choices and live with those consequences, so make them well.”

And what were hers? “I wanted to be a parent and to be around. I didn’t want to miss out on their childhood. It meant it wasn’t about me anymore.”

Was that hard to concede? “You respond to what you have in front of you and my family comes first, so I just work around them and do my best with that.

“So work is a luxury, and while I am 100% committed to it, I could let it go in an instant.”

And yet Hermione’s work ethic is legendary, so has that altered as well?

“Honestly and truly, having a focus and commitment to my work has been my anchor. What I work on centres me and I still have the same level of commitment. It has been a very important thing in my life.

“But then I don’t know how to do anything else and from a practical point of view you have to earn money.”

Future plans are therefore pie in the sky, but she admits: “I would like to write and direct my own work, and theatre is another thing that’s too difficult at the moment because I don’t live in London anymore, so when the children have left home I’ll probably spend all my time on stage.”

“But in the meantime I have a 13 and a 10 year-old and am at full capacity - even the goldfish seems can send me over the top,” she laughs.

Having decided on acting from an early age, her determination to realise her dream is put into context when it transpires that Hermione’s childhood was somewhat haphazard.

After her parents split up, her mother had to work full-time while she and her three sisters ran the house and looked out for each other. Her father remarried and she also had two half-sisters.

So perhaps creating order out of chaos is something that Hermione’s unruffled character takes great pleasure from both on and off screen?

“It is an extraordinary thing to have that level of determination as a child, but I always knew what I wanted to do, “ she agrees.

“From a very early age I wanted to be an actress and I got into Elmhurst Ballet School, where a drama teacher championed me and encouraged me to apply to LAMDA. I was absolutely determined despite the fact that 95% of actors aren’t working.

And now? Would she encourage her children to become actors?

“No, no, no. although I will support them in whatever they decide,” she says. “It is such a brutal industry, even though I have been very fortunate. There is no certainty and it takes no prisoners. You are utterly dispensable. But nothing could have changed my mind.”

In the meantime Hermione has to return to the set of Luther. So is she looking forward to coming to Oxford or will that be work too?

“No, I love it there because my husband was at university in Oxford so I always see it through his eyes.

“We’ve been together for 14 years and he’s in the business too (Simon Wheeler is the screenwriter and TV producer who created the ITV1 drama Kingdom and wrote Wire in the Blood, which starred his future wife) so he doesn’t bat an eyelid about what I get up to on screen, which is wonderful and very levelling.”

Including all that on-screen romping? “Yes, including the romping,” she laughs