Best-selling Young Adult book The House With Chicken Legs is brought to life at New Theatre Royal, Portsmouth

“I’d been writing for 10 years, mainly for my own children, and purely for the love of it,” she says from her home in the Lake District.

So when her YA novel The House with Chicken Legs was accepted for publication, and quickly became a hit, it came as something of a surprise.

The story centres on a 12 year-old girl, Marinka, who lives with her grandmother, the mythical witch-like Baba Yaga, in a house with legs that moves every few months. It was inspired in part by the stories Anderson was told by her Prussian grandmother, who fled eastern Europe during the Second World War.

“Like so many people she lost everything during the war, so the stories and music she carried with her were extremely important,” she explains.

“My grandmother would tell many versions of the Baba Yaga tales, and they were always my favourite. She’s a fascinating and wonderfully ambiguous character.”

The House with Chicken Legs was published in 2018 and was shortlisted for a number of prestigious accolades, including the Carnegie Medal and the Blue Peter Book Awards.

Anderson says she found its success “mind-boggling”. “I honestly didn’t think anything would happen with it. I even remember my agent saying, ‘I’m not really sure how big the market will be given that it’s about death’.

But before it was published it was chosen as Waterstones book of the month, and then teachers started to embrace it as well, which was wonderful.”

Further good news came when she was approached by leading theatre company Les Enfants Terribles about the prospect of a stage adaptation.

“It immediately felt right,” says Anderson. “I thought the aesthetic of their work fit the story so well, and when they sent further thoughts about their vision for the production, the more excited I became.”

The show premiered at Manchester venue HOME in 2020, and was quickly acclaimed by critics for its originality and flair.

The story is vividly brought to life using puppetry, projections, music and masks. Anderson says that, when she first saw it, she “cried pretty much all the way through”.

How did it feel to see the characters she’d created coming alive in front of her? “The cast are all so awesomely perfect,” she enthuses.

“And there were some strange coincidences-for example the character of Marinka was quite heavily based on my daughter, and the actor who plays her, Eve [De Leon Allen], looks similar to her. They couldn’t have known that when they were casting, but they got it spot on.”

She is equally effusive about the adaptation by Oliver Lansley (who also directs the production, with his Les Enfants Terribles co-founder James Seager).

“He totally recognised and brought out the essence of the book,” she says.

“But he also drew out other themes and enhanced them, such as the importance of individuality. He’s also widened the Yaga folklore and made it feel more global. I think it’s really wonderful how it feels both true to the book but is also very much its own thing.”

The production, which won an Offies Award for excellence in theatre outside of London, is returning this year for an 11-venue UK tour, culminating in a run at the Southbank Centre’s Queen Elizabeth Hall.

Anderson says she is thrilled that the show is getting a chance to reach a wider audience. “I’m especially pleased that a lot of school children who have studied the book will get to experience it, and see how Les Enfants Terribles have worked their magic.”

For the tour, the company is partnering with the charity Cruse Bereavement Support, who provide care and campaign for better awareness of those suffering grief. It’s a cause very close to Anderson, who wrote The House with Chicken Legs to help her come to terms with loss in her own family.

"I’d experienced a lot of grief, and to be honest I hadn’t dealt with it very healthily,” she says.

“The reason I struggled was because I didn’t seek help. I think in our culture too often grief is something people think they just have to get on with. But Cruse is a brilliant organisation which shows that support is available.”

She adds that she is moved by the number of people who tell her how much The House with Chicken Legs has helped them.

“I often have Zoom calls with classes of schoolchildren, and they tell me what it means to them. I also get messages from grown-ups telling me how it’s helped them through grief, and even that they’ve used the death journey words from the book at loved ones’ funerals. I feel very honoured that the story has helped people in this way.”

Life for Anderson is busy (or, as she describes it, “chaos”); she has four children, three of whom she homeschools, so her work has to fit around these commitments.

But she’s recently found some structure thanks to a daily Zoom call with a group of writing friends, who write together every morning. “It’s the first time in over 15 years of writing that I’ve had any kind of writing routine,” she says.

“But I’m always thinking about stories, whatever else I’m doing. Writers never fully switch off.”

It’s impressive that she’s managed to publish four books in as many years. And this autumn sees the launch of her fifth, The Snow Girl, which is inspired by classic Russian fairy tale The Snow Maiden.

It will be her first hardback, featuring sumptuous illustrations by Melissa Castrillón, who also designed the cover for The House with Chicken Legs.

“I wanted to write a magical, wintry, family story,” she explains. “I set out to write for a wide range of ages, something that was good for reading at bedtime. Like all my work it’s based on a fairy story, but has a bit of a modern twist. Hopefully it’ll be on a few Christmas lists!”

With that, she has to get back to her hectic schedule of work and homeschooling.

Just like Marinka’s house, she’s come a very long way in a short space of time, and doesn’t show any signs of slowing down.

It is at New Theatre Royal, Portsmouth on November 2-3. Tickets £23.50. Go to newtheatreroyal.com.