Eric Carle is a legend. He has sold 110 million books to date and has kept generation after generation of children entranced with his wonderful stories and illustrations. Katherine MacAlister catches up with the octogenarian on the eve of his most famous book The Very Hungry Caterpillar debuting as a play at The Oxford Playhouse.

Eric Carle is not only one of the most famous authors on the planet, but his own life is just as fascinating as those of his fictional characters.

Born in the US, his German mother returned to Germany just before war broke out.

His childhood was spent surviving the Nazis and, at 15, Eric was sent to dig the Siegfried Line.

The family later returned to the US where Carle went on to become a successful advertising executive, until a canny colleague glimpsed his illustrations and asked him to write a children’s book.

The rest is history.

And yet Carle is still as passionate about his books today as he was in 1967, and says that his wartime experiences were hugely influential in his writing.

“I think about Germany and my childhood there during the war quite often,” Eric tells me quietly. “Growing up during the Second World War in Germany left me with painful memories but the colourful illustrations of my books are a kind of antidote to the greys and browns of my childhood.”

You’d never know when turning the pages of his colourful books that they are a form of therapy, but he, of all people, understands how hard it is sometimes for a child to fit in.

“I am especially interested in a child’s transition from home to school,” he says, “because this can be quite traumatic. For me it was a particularly difficult period in my own life.

“I started first grade twice, once in the US and once in Germany, both at the tender age of six.

“Two cultures, two languages, two different teaching methods. So I hope my books will be entertaining, interesting and pass along some learning, as well as making this transition easier for children.

“Because my books and stories are connected to the child in me, and this is where I always begin,” he says.

It was the time he spent with his father, that, out of all his life experiences, most influenced Eric Carle, demonstrating that “quality time”, as the Americans love to call it, matters.

“I have always loved animals and insects and my father used to take me out into the woods when I was a very small child.

“He would peel back the bark of a tree and show me the creatures who lived there. Little crawly things. So I am inspired by nature.

“But inspiration and ideas for books can come from all kinds of places. Dreams, memories...”

Is this why they are so successful?

“I think my books are hopeful and perhaps this is why they continue to be enjoyed by so many people,” he says. “And it is this hopeful feeling in the pictures and the stories that have struck a chord.”

The most successful of Eric’s 70 titles remains The Very Hungry Caterpillar.

“It is my most well-known book,” Eric agrees, “and it also has a special place in my heart because it was one of the first books I both wrote and illustrated.

“It has sold over 33 million copies and one of my staff calculated that one book has sold every minute somewhere in the world, every day and night since it was first published in 1969.”

It is also the book chosen by the Mermaid Theatre Company to convert into a children’s play. “I am a great fan of theirs and think they create a delightful performance of the stories while honouring the simplicity and integrity of my books,” Eric says.

“But Do You Want to be My Friend? is my favourite book because it is about friendship, which is very important to children. To me, pictures need writing and writing needs pictures. A child once called me a picture writer, and that’s a good way to describe me. It is the idea that comes first.”

And, of course, ideas never stop, however old you are. “Stories have a way of coming together when I least expect it. I am retired now from the business end of my work and am enjoying spending time with my wife Bobbie, friends and family. But I don’t feel I can truly say I will ever retire from creating books because after finishing a book, I feel a sense of completion and entertain the idea that it may be my last book, that I have nothing left, but then a new book will make itself known. Each book is different. Some books come together very quickly, like being struck by a bolt of lightning. Others take years for the idea to form.

“But I think of all of my books as my children. And I usually write my books for the child I once was, for the child inside.”

* The Very Hungry Caterpillar runs at the Oxford Playhouse tomorrow and Saturday. Call the box office on 01865 305305.