I had been worried a few months after my wife died about many things: her family’s wellbeing, my own health and ability to survive it all, even the practical necessities of my work and managing the family finances.

Most of all, though, I was worried about my daughter, Romy. She was only six when her mum finally succumbed to cancer after nine years. Bereavement just seemed too much for a young child. Too vast. Too complicated. A great weight on very small shoulders.

Then there was the fact that Romy had always been quiet and self-contained – inscrutable, undemonstrative. I worried that she was holding all her grief in, too tightly. I wanted to help her let it out but I wasn’t sure how. I had no experience of anything like this. I felt ill-equipped. I had spoken to some teachers at school, I had read some books on the subject, I knew some theory but still felt very inexpert, even that I was making things worse, forcing her into further and deeper retreat. I wanted to be a good dad when she needed it most.

I tried to talk to her directly about grief but she mostly changed the subject. I tried being open with my own emotions, as if showing her how to grieve, giving her an example to follow by deliberately showing how very upset I was on certain occasions. Still she seemed implacable and didn’t shed many tears.

Then one day, when we were playing with some cardboard boxes in the hall, she expressed an interest in “making” Mummy. I didn’t quite know what she meant till she put the largest of the boxes on top of a nearby chair and a smaller one on top of that. You could start to see a head and a body in outline, as if a person were sitting down.

I got some cardboard tubes out of recycling and fixed them to the larger box with sticky tape. They looked like arms. I attached more cardboard tubes further down and suddenly the figure had legs. Romy started drawing on a face, lips and teeth. I cut a mouth out of the head with a bread knife. Before long, we had a new member of the household – Cardboard Mummy.

Light, adaptable and with a perfect square bottom that meant she could balance on any flat surface, we sat Cardboard Mummy at the table while we ate, brought her in the living room to watch TV with us and carried her upstairs to listen to Romy’s bedtime stories and sleep alongside her. She became a confidante, a constant companion and a comfortingly reliable presence. Cardboard Mummy was referred to, asked her opinions, and generally included in the conversation.

Carl Gorham with Romy.

Romy seemed happy and I was too. Something was happening here. Something was being expressed. It all felt positive, if mysterious, and that felt good. But I worried a little as well. Was I being a wacky, irresponsible, self-indulgent dad who should have been helping his only child face the reality of an awful situation instead of playing with cardboard? Was I letting my daughter live in a strange fantasy world full of delusion instead of hard fact? I spoke to a child psychologist who said it was not uncommon for children to build effigies or dolls, that it was a natural expression of loss and longing. The advice was to go along with it all, however strange or weird it might seem – and I did, even if sometimes with a tight smile and a clenched jaw.

As time passed, Romy grew more ambitious, wanting to take Cardboard Mummy out – to the shops, to meet friends. Other parents seemed to become aware of Cardboard Mummy. She became a public figure. She travelled in the front seat of the car with the seat belt on.

I liked the fact Romy seemed happy about all this but I found my own discomfort growing more as well. To me, it sometimes felt that our little domestic experiment was getting out of hand. As if something that should have been a family matter had been kidnapped by the world. I started to feel more and more self-conscious whenever Cardboard Mummy left the house with us.

Mostly it was concern about Romy’s own vulnerability. I worried about how the comments of others might affect her. And the more public Cardboard Mummy went, the more Romy might be exposed to such things. I felt a loss of parental control.

Partly too, though, I have to admit it was my own self-consciousness. Seeing that look in a fellow parent’s eye. That momentary flash of disbelief that seemed to say “OK. Wow. Well … a mummy made of cardboard. That’s … er … different!” that made me wince. As if I were a bad parent, who should have been protecting his only child, not directing his own Hitchcock movie.

Then one day, Romy wanted to take Cardboard Mummy to school for a show and tell. I agreed but was concerned about how it would go, my daughter with her strange Cardboard Mummy in front of an audience of six-year-olds. Kids can be brutal at that age, unflinchingly direct. Merciless. Even cruel. I worried all day about their reactions. I imagined various hurtful comments and her returning home chastened and upset. Ready to retreat even further into the emotional shell from which she had only just started emerging.

Yet when I arrived at school, I found it had been a triumph.

As her teacher explained, Romy had brought Cardboard Mummy to the front of the class and talked about her mum dying and how sad she was. And how she chose the dress her mum wore in the coffin and a song for the funeral. All the things that I had worried were buried down, deep inside her and locked away for ever.

Over the next few weeks and months, Cardboard Mummy seemed to become less important. She became tatty and dilapidated. After a while, we moved her into the attic where she remains.

That day didn’t mark the end of something but when I look back now, nearly 10 years on, I still think of its significance. A big occasion for a quiet, gentle girl, the moment when a lot of her grief suddenly found a voice. Bereavement is a lifetime’s project and as Romy gets older she will doubtless encounter many roadblocks on the way. Moments when she feels stuck, emotionally in chains. My hope is that she thinks back to that extraordinary time and finds strength in those memories and her own courage.

In those dark moments when you worry about your child, maybe you should believe in them more and worry less. Trust them. They have their ways. Even at six. They are resourceful beyond their years. Instinctive. And in a way, brilliant. They use what they need. They are great survivors.

Romy is now 15. An intelligent, purposeful, mature young woman who is balanced, thoughtful and kind. She will always miss her mum but she is going to be fine.

And a simple cardboard effigy, made from boxes and sticky tape, is one of the reasons why.

• The Owl at the Window by Carl Gorham is published by Coronet, £14.99. To order a copy for £12.74, go to bookshop.theguardian.com or call the Guardian Bookshop on 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.