I was hiking alone in the remote mountains of southern California and, to begin with, it was just a beautiful walk in the forest. I was following a trail beside a stream. The trees were such a brilliant green, the sky so deep a blue, that it almost hurt to look. I smelled pine resin. I heard the chatter of a jay. It was one of those perfect days.

Suddenly, everything changed.

On the other side of the stream, I spotted two boulders. Except - they weren’t boulders. They were bear cubs. I didn’t have time to think how sweet they were, because the next moment I saw the mother: a huge black bear moving down the slope with awesome grace. Moving towards the water.

Towards me.

My heart began to pound. An old rancher in Wyoming had warned me that a female bear with cubs is at her most dangerous. If she thinks you’re threatening them, she’ll attack. He’d also said that as bears can’t see too well, and hate surprises, it’s vital to make a noise to let them know you’re there. His tip was to whistle or sing.

Well, I can’t whistle, so I didn’t have much choice. And although the bears weren’t far away, I could tell from the way the mother was nosing around that she hadn’t yet spotted me. My way home led right past her. I couldn’t hope to sneak by, as she’d be bound to smell me, and think I was hunting her. I had to let her know that I was there. So I took a deep breath and launched into the old Irish song “Danny Boy” (shakily, and without the words!).

Instantly, she swung round: ears pricked, all attention focussed on me. She can’t have liked my singing, because instead of turning and going away, she left the cubs where they were, and started purposefully across the stream - towards me.

That’s when the fear really kicked in. That’s when my mind went white. For a few seconds I couldn’t see anything. Couldn’t hear anything. If I made a wrong move, she would attack.

Standing there facing her, I realised just what a puny thing a human being is. I had no defences. I couldn’t run faster than her, and I couldn’t climb higher. If it came to a fight, I wouldn’t stand a chance; she’d snap my neck with one swat of her paw. All I could do was try to speak her language, and somehow get across that I was neither a threat to her - nor something she could eat.

By this time, she’d stopped in midstream, a few feet away. She was so close that I could see the pale, silky fur inside her ears. She was really agitated: hissing and huffing, and rocking from side to side, as if considering whether to rise up on her hind legs and attack me.

For an endless time we stared at one another. I’d stopped singing. My mouth had gone dry. My heart felt light and fragile in my chest. I could hardly breathe.

Very, very slowly, I began to side-step past her, not showing my back, and talking quietly, to calm her down. At least, that’s what I was trying to do, but my voice was shaking so much that I don’t think I did much good.

Still rocking, she watched me go, never letting her eyes off me. Finally, after a lifetime, my path dipped out of sight - and I ran like crazy. I ran all the way down the mountain - I was lucky not to break my leg - and as I ran, I kept glancing back, expecting to see her coming after me. I never saw her again.

That was the most terrifying experience I’ve ever had. But it also felt, weirdly, as if I’d been back in time. In those moments when I was facing the bear, thousands of years of civilisation vanished like a wisp of smoke.

She didn’t care who I was, or where I came from. I was in her world, not my own. I could have been a person from the Stone Age.

I never forgot what it felt like to face that bear. A few years later, I was thinking about writing a story about a boy and a wolf, and struggling to find the right setting. Suddenly, the memory of that day in the forest came flooding back. “The Stone Age,” I thought, “of course! It happens in the Stone Age!”

Writers don’t often get that bolt-of-lightning feeling, and when it comes, it’s as well to pay attention. I dropped everything, and started to write.

The result was Wolf Brother.