This morning I got on the bus, the last of a clutch of people waiting at the bus stop. My oyster card was rejected, and as I looked through my pockets for change I knew I didn't have the bus driver pulled away.

I told him I didn't have the fare and he said I'd have to get off at the next stop, so I waited at the front of the bus as it trundled through the traffic.

Then a complete stranger, a woman of about 50, with one of those old people's shopping cart things and a cockney accent shouted to me "eey-ar mayte!" going into her purse. I protested - I could easily have topped my oyster up in a shop and got on the next bus -but she insisted. She wouldn't even take back the extra 10p she gave me by mistake.

This has made me feel very good about humanity. Never seen something like this happen in London before.

What good deed should I do to humanity in return?