Pam Ayres is best-known for her jokes and crackpot poetry. But you will search in vain for either in her latest and longest work. “No, I cannot think of even one,” she admits, stopping for a moment in front of the gleaming four-oven Aga in her Cotswolds kitchen.

“I tell you what,” she says, her Gloucestershire sing-song growing even softer, “I am approaching 50, and in my middle years I have decided not just to write what people expect of me. For a long time I’ve tended to do what people expected - which was comedy - but I always wanted to try some serious stories. This is one of them.”

The Nubbler is “a proper novel” on the subject of divorce as seen and experienced by a ten-year-old boy called Rufus. The book is strongest in describing the breakdown of a marriage but it also has much to say about friendship and teachers. Rufus is guided and comforted throughout by a strange little creature called the Nubbler, who listens in to the world through a headset.

“I heard you crying,” says the Nubbler on a typically dark and stormy night for Rufus’s parents. We readers already know all about it. “Downstairs his parents raged. Rufus could hear their furious, shouting voices, his father’s loud and blunt like a club and his mother’s high, jabbering, the way it always went before she burst into tears, before his father stormed out of the house.”

The fight scenes are particularly evocative and will strike a chord with anyone who has sat in another part of a house and listened to the grown-ups shout and scream the same sentences they have shouted and screamed before. It’s not much better when the shouting is finally over. “Rufus curled up, hugging his frozen legs, hating the feel of the house, the bitter words that hung in the air, the fear of it all starting up again when his father eventually came home.”

Can this be by the same woman whose other new book, With These Hands, contains poems about the Wonderbra and the National Lottery?

The answer is a quick but quiet yes. “I feel desperately sorry for children in Rufus’s situation,” she says. “My father is gone now and my mother is 83. I had two wonderful parents who loved me and gave me a good childhood and I am not criticising them in any way. But they did have a fairly stormy relationship.

“There were large arguments that I remember because they were so frightening. It’s one of my earliest memories. I remember lots of happy things too, but every once in a while these rows would blow up and there would be this terrible atmosphere. You just do not know what to do and you feel helpless.”

In the book, Rufus feels much less helpless once the Nubbler comes to visit. This creature - part dragon, part dog and part seahorse - is magical and imaginary all at once. He can make himself disappear and predict the future. This means Rufus can see that things are going to change and that divorce is not the end of the world.

“This story is written from the heart - and I hope that does not sound posey. I wanted it to be reassuring to children who are in that situation. It doesn’t last forever. You think at the time that you are going to be trapped but gradually chinks appear where you can start to make your own life.”

For Rufus that means making friends with the new boy at school and getting to know his teacher, Mr Carmichael, who often seems too good to be true. In fact, the book is populated with quite a few such characters and the ending is almost ferociously optimistic. “It’s a bit more sugary than most children could hope for,” she admits, “but I did make it optimistic because I prefer that.”

Her own ferociously optimistic ending would involve someone making a film of The Nubbler. Not just a television programme, mind, but an ET-type Hollywood movie. “Well, you have to set your sights high, don’t you?” she asks.

What that means for Pam Ayres is getting down to the funny business of being serious at last.