Five-minute memoir: Isabelle Grey is driven to distraction after passing her test

On the open road, Isabelle Grey was ready for anything. Except this.

I had recently passed my driving test, it was the start of the school holidays, and I was allowed to borrow my mother's car for a solitary 40-mile excursion. It was a summer's day, the café was crowded, and I shared a table with a motherly woman. I liked then to drink cold milk, and she remarked on it, telling me she was a farmer's wife.

My father's idea of childcare had been to take us into the hospital where he worked, tiny apprentices trotting at his heels, so I had been taught early on how to listen to people. Maybe it was that, but, in exhaustive detail, she began to tell me how they kept a donkey, silly really for a hardworking farmer to keep an animal as a pet, but her son loved the creature.

I forget now how it came about in her story, but, against her own better judgement, the donkey, now getting on in age, was in foal. One night, there was a storm and, in a stable with only the light of a kerosene lamp, the donkey had difficulties giving birth. The vet was elsewhere, priority given to animals on which a fellow farmer depended for income. He arrived too late, and the donkey died. The farmer's wife did not spare me the gory details – blood and rainwater and straw in the yellow kerosene light – of how the foal could not be delivered, and how terrible it was to her, female to female, to witness the agony of her donkey's hopeless labour.

She was never sure whether, even if the vet could have come sooner, anything different could have been done. Perhaps I've remembered wrong, and the foal did survive, but they didn't keep it. Did they bury the donkey in the orchard, or have I made that up? Either way, her husband thought it sentimental to grieve over a donkey.

She wept, people in the busy café turned and stared, and I felt hot and awkward. I had observed my father often enough as he broke bad news, comforted relatives, or kept silent and nodded in sympathy. Maybe I had a good bedside manner.

But this was not the adventure I had wished for when I set out. My mother had been happy to lend me her car. After all, she had first taught me to drive when I was 15 on hidden back roads in the Lake District where she had once driven an old army jeep, visiting patients on remote fell-side farms. They'd been her happiest days, and, in teaching me to handle a car, she'd been able to share her now overshadowed exhilaration and confidence.

The A56 to Chester was not Route 66, and I was behind the wheel of a Ford Escort estate, not the Great White Shark. But still. I was 17, allowed to dream that, with Kerouac, I was on the road. Yet now I was embarrassed that my adventure amounted to so little. I'd wanted… at the time I didn't even know what my hopeful young self wanted or expected from a sixth former's day out in Chester, but now this woman and her story and the people staring had exposed my foolishness.

I escaped to the Ladies, but when I returned, she had ordered me a second glass of milk. Ashamed of being too well brought-up to rebel, I sat back down. She had composed herself, and wanted to know if she could ask me a question.

I was beginning to sympathise with her husband. I had been raised unsentimentally: this was a donkey that had died quite some time ago, and I wanted to be gone.

My impatience was transformed as she told me how her son had been killed in a motorbike accident nearly three years before. She outlined the facts in the police report: mid-afternoon in clear, dry weather, at a crossroads he swerved to avoid a car that failed to see him, lost control and hit a telegraph pole. He died instantly. Her voice was steady and she did not shed a tear. I began to fear what her question might be.

Her husband had dealt with everything. She'd been in shock, ill with grief for a long time. She barely remembered the funeral, what flowers there'd been, who had come. His friends, certainly. He had a lot of friends and they'd been very kind. But she had never been to the crossroads where it happened. There was nothing to see, and her family thought she'd be too upset, yet it felt wrong not to visit the place he died.

What did I think? I was around his age. Should she go? Would he want her to go? She waited calmly for my answer. I was unqualified to respond, just a second opinion. But I was sure she wanted to go.E

'The Bad Mother' by Isabelle Grey is out now in paperback (Quercus, £7.99)