'I am sure turning 50 will hit me with a jolt, but I don't feel there will be a huge change... it is how you feel inside that matters, and I feel about 27'
Bestselling author and mum-of-five Sophie Kinsella talks to Hannah Stephenson about family life, her next movie and why reaching her half-century holds no fears for her at all
She rose to fame with her bestselling novel The Secret Dreamworld of a Shopaholic, published in 2000, but a lot has happened for Sophie Kinsella since those heady early chick-lit days.
It's 10 years since that book was adapted into a movie, Confessions of a Shopaholic, starring Isla Fisher as heroine Becky Bloomwood. In that time, Kinsella's family has expanded (she has five children), she's had more bestsellers and her 2003 novel, Can You Keep a Secret?, is about to become a movie, starring Alexandra Daddario.
More than 40 million copies of her books have been sold in more than 60 countries, translated into more than 40 languages. She's branched out into Young Adult novels, too, along with the first in a series of illustrated children's books.
Kinsella, who began her career writing under her real name, Madeleine Wickham, turns 50 this year and remains as upbeat and bubbly as her characters, writing romantic, light-hearted books featuring young heroines in love-torn situations.
She's certainly keeping pace with the younger generation, posting pictures on social media of her recent attempts to surf in Tenerife for the first time - a pursuit she loved - and with more than 38,000 followers on Twitter and nearly 53,000 on Instagram, even her children are impressed.
"I remember once, they saw one of my Instagram posts and said, 'Wow! That's a lot of likes!' Just for one moment, I was 'Cool Mum'."
Her latest novel, I Owe You One, centres on 27-year-old Fixie Farr, who helps run her family business, a general store, but is clearly a woman looking to find her voice, as she wrangles with a bossy brother and tries to live up to her mother's standards.
"There's always something of me in every character I write. I drew on university experience (she went to Oxford), when I used to sit in tutorials and there would be lots of confident types who would just say what they thought and they didn't care if they were wrong," Kinsella recalls.
"I was the opposite. I would sit silently, having thought of arguments and responding to points in my head, but rarely daring to say them out loud."
Fixie has the chance of romance when she saves a handsome stranger's laptop from being destroyed by a flood in a coffee shop. When he scribbles her an IOU as a thank you, it's fate that their paths will cross again.
But so besotted is she by her leeching, narcissistic teenage crush ex-boyfriend, who returns home from Hollywood needing a job, that she unwisely calls in those favours.
"I have seen that blindness that comes over you when you're so convinced that this is the guy for you, that you make every excuse under the sun for him. Having been on the periphery of relationships like that, you just want to say to your friend, 'Really?'" she observes.
Kinsella herself has been married to Henry Wickham for more than 25 years. Two years ago, he gave up his job as a headmaster to help manage his wife's career, which continues to flourish.
As well as the books, which she writes from home in London, the film adaptation of Can You Keep a Secret? is now in post-production.
Kinsella was less involved with this one than the Shopaholic film, she says, although she did go on set in New York.
"It was fantastic. There was a great atmosphere, everyone was having a good time and the scenes I saw being shot were so funny. I'm excited."
She may have been a little starstruck by the movies, but her large family has kept her grounded, she reflects.
"I've got more confident as the years have gone on. Having a family has grounded me and given me perspective. When you have a large family and are concerned about so many lives, your own life just becomes part of the family.
"What's the worst thing that can happen? I once arrived at an interview and I hadn't done up my dress, which was completely open. But are my children going to love me any less? No."
She says she always had romantic notions about having a big family, sort of like a British version of The Waltons, but the practicalities were different.
"We had two children and for a long time, I thought, 'That's it, we're too exhausted to have any more'. But we started quite early, which meant that after some time had gone by, we were able to consider that we did rather love bringing up children and we had time to have another one. And somehow another one turned into three more."
She has four boys and one girl and there's a 15-year difference between her eldest, aged 22, and her youngest, seven-year-old Sybella.
She admits that she's become a more relaxed mother with age.
"Having seen two children through education, you realise that everything will be fine and not to get too stressed out about these tiny things that seem so important when you're doing it."
She was 42 when she had her daughter.
"I feel very lucky to be enjoying motherhood at this age. With my first baby, I was the youngest in the NCT group. Now, I would very much be the oldest. I was concerned if I could physically manage it, but I was fine. But I do want to take care of myself more as a result, because I want to have the energy to be the mother of young children. It's lovely for me to be able to do this again. It feels like an absolute blessing and it keeps you young."
While other authors who began their careers writing chick-lit have since moved into the mum-lit genre, writing about the issues that face women as they get older, Kinsella has continued to write about younger 20-somethings.
"I do quite like the dynamic of somebody on the brink of life with horizons stretching ahead. And in terms of the workplace, I was a journalist, very much the junior in the corner watching the big ones. I did a job at two different magazines as the junior and then I left to write novels.
"In my head, I'm forever the junior in the corner. I never went up the ranks, or became the boss, so I find it quite easy to tap into that level of progression. It's an interesting stage, because so much is still up for grabs."
And she hasn't yet contemplated turning 50.
"I'm sure it will hit me and I will suddenly have a bit of a jolt, but I really don't feel there will be a massive change in my life," Kinsella reflects. "It's how you feel inside that matters, and I still feel about 27."
I Owe You One by Sophie Kinsella is published by Bantam, priced £20