It was a Tuesday in November. I was at the supermarket checkout with a week's worth of shopping, a long queue behind me, and a card that decided, without warning, to stop working.

The cashier tried it twice. Then three times. By the fourth attempt I could feel the heat rising in my face. I was apologising, fumbling for my phone, trying to remember if I had another card, quietly calculating whether I could just leave half the shopping behind.

I turned to him immediately. Told him I couldn't let him do that. He shook his head and smiled — not unkindly, just firmly — and said: "It's fine. Pay it forward someday."

I asked for his details so I could transfer the money. He refused. I asked his name. He told me it didn't matter. The cashier processed his card. He picked up his own basket and moved to another till. By the time I had gathered my bags he was already gone.

I have paid it forward four times since that day. Each time I do, I think of him. I still don't know his name. But I know exactly what he gave me — and it was worth far more than the groceries.

He gave me the reminder that kindness doesn't need an audience. It doesn't need a name. It just needs someone willing to step forward.