Dorothy Judd who was stopped by the police when she was playing with her grandson as they thought she was doing something inappropriate.

Max lies on his back, looking up at the high canopy of beech trees. We listen to the sounds of birds, the muffled roar of traffic, children's voices, some loud bangs in the distance."I wish we could sleep here," he says. "Can we?"

"It would be lovely, Max. But I think we'd get cold. And it would be hard to sleep out here. But when you're older I'm sure you can go camping," I reply, pleased that he feels so relaxed and safe. But that's how it should be when you're five and with your grandmother.

We had come to these woods the previous afternoon as well. They border a vast park in a suburb of a northern city. Quite wild and muddy, the woods are sordid with litter, but nature triumphs with abundant fungi, ivy, brambles and the extraordinary roots of vast trees that Max had climbed on. He had chosen this outing because he, and I, did not want to watch rugby on television with his brothers and grandfather. We, the grandparents, are in loco parentis while his parents have a rare short break in Venice.

The previous day I had been concerned that we might be vulnerable in an isolated part of the woods, so I had steered us to an area near a main path. Here, people walked their dogs and there were passers-by every few minutes. Many smiled, some said hello.

"Granny, do you know those people?" "No, we're just being friendly," was an exchange that took place between us a few times. I didn't think about the people who didn't acknowledge us.

Earlier, in a supermarket, Max had been obscured for one second behind someone else. I'd felt a panicked "What if . . .", before seeing him again. I realised that as a grandparent I felt extra vigilant, having been entrusted to care for him and his brothers - probably more so than I had felt with my own children when they were young.

In the woods, we began to create a den, as we had done months before with other members of the family. We collected branches and sticks, planning the doorway, the interior, the functions of the space.

This was a modest den, not much more than a primitive tepee, with open sides and large logs marking two "walls", but to Max it was a house with a front garden. He felt inspired to make a doormat with a flat stone, to build a fireplace and to collect more stones in order to make - all by himself - a beautiful work-surface on one of the logs for our kitchen. I joined in, pleased he was so happy and imaginative; pleased he could still do some of the things - with an adult, of course, nowadays - that I used to do as a child when one had greater freedom; pleased that he didn't mind slugs, worms or mud on his hands. Seeing his small frame ahead of me, nimbly stepping over branches, roots, and stones like a woodland elf, I knew that this was another blessed moment in my store of beautiful times granted by our grandchildren.

Our afternoon passed rapidly, "cooking" mushrooms over the "fire" with "chopsticks", finding a very old mobile phone without a battery, a few beautiful bottles and a ball, all of which Max wanted to keep.

"Why so many seagulls when we're not by the sea?"; "How deep is the water?"; "Who was your best friend when you were little?" were just some of his questions as we wandered back, hand in hand, Max with his plastic bag of treasures slung on a stick over his shoulder.

The following afternoon he wants to repeat the outing, and we are both delighted to find the den exactly as we left it. This time he cooks "deer" with "lettuce", then makes a pillow out of a mossy stone and pretends to go to sleep while I sit nearby.

"Max, we should be going back soon," I say eventually. "Time for tea soon, and we can all watch Mr Bean's Holiday . . ."

"Police!" says Max, sitting up in astonishment.

I turn around to see a very large policeman in a fluorescent jacket approaching across a rough patch of ground. He asks what we are doing. "This is my grandson, Max. We're making a den, as you can see. But I was just saying we should be getting back for tea."

"You all right, Max?" he asks.

Max looks bemused and rather shy. "Yes," he says quietly, glancing up at me inquiringly.

The policeman says that there have been two reports, two separate contacts, from people who are worried, suspicious, as to what is going on. Max comes and stands by me, looking up.