It's easy to find a good deed to do on the road. We left donations at temples, museums and other attractions. We didn't bargain too hard. We ate at a restaurant which serves as a hospitality training centre for disadvantaged youth. All this was well and good. And then. Then came the night of the lottery tickets.

We were sitting in a coffee shop in Da Lat, drinking what is arguably the best coffee in the entire world, when an old woman came in - not begging, exactly, but selling lottery tickets for a small commission, which is a pretty close thing. As one of our guides explained, Vietnam has a daily lottery draw, which happens somewhere at 5pm. Tickets are about 35 US cents each, results are published in the national paper, and there's a cash prize. On a whim, I bought a couple of tickets. It took me a few moments to dig for the cash, and I chose my tickets from the bunch offered me, with a quick thanks. And then.

Then I happened to glance up into the woman's face. She was grinning with excitement. She said something in Vietnamese, and grinned some more. Her eyes were shining.

Later on, they started to close up shop, so we asked for the bill and made to leave. "What are you going to do with the tickets?" Mr Bea asked. Tracking down the winning numbers seemed an impossibly large effort for a fairly small and unlikely payoff. So when the waitress came back I gave them to her. She looked at them, and got that same grin and that same shine in her eyes. She asked whether they were really for her, and I said sure, why not, so she went off to show them to another waitress and we watched them talk excitedly.

It was strange. The reactions seemed all out of proportion to what we'd given. There was something about those little bits of paper - the potential, I suppose, the anticipation. There was some sort of magic in them.

And then.

Then I got that feeling again. The one where it's ok if we don't have any kids, because I can still experience that look on someone's face - the bright, shining eyes, the excitement, the magic. And I thought, pish tosh to all those who say there's nothing like the wonder of watching your child grow. Perhaps they've never bought lottery tickets from an old woman in a coffee shop in Da Lat.

Now if you'll excuse me, I have to buy a return airfare's worth of carbon credits for deed number twenty-eight.