It was when I read a letter from a Times reader last month that I felt we'd turned the corner. “The Times has wonderful diagrams,” John Riddall, from Derbyshire, wrote. “Rarely was a diagram more needed than to illustrate the working of the elephant pump. I wonder whether you could publish a diagram as part of the continuing publicity for the appeal?”

We did then publish a diagram. This had been exactly the sort of response I had wanted to stir when reporting from Malawi about Pump Aid's work in Africa. For at the heart of this small British charity's mission is not love, or understanding, or any of those warm words in which too much feel-good charity talk is couched. At the heart is something small, hard, practical and real. A clever Englishman and two colleagues from Zimbabwe dreamt up a way of hand-pumping water out of a well that costs a tenth of what a traditional piston pump costs, does the job just as well, and can be put together from little more than some standard PVC piping, some rope, a winding wheel and a pile of bog-standard rubber washers.

The problem: open wells and old buckets spread disease but a closed well needs a pump. Piston pumps are expensive and need expert maintenance. The solution: Pump Aid's elephant pump. And that's it. No need to tug at the heartstrings. No need to moralise. No need to tell African women why they ought to want clean water: they already do, desperately. No need to tell Times readers why they ought to want to make life better in a poor continent. They already do; but they also want to believe that money pledged will make a difference. Well, this pump (and Pump Aid's waste-munching latrines) will do that.

News of our success in fundraising for Pump Aid will surprise and delight the charity. It delights but does not surprise me. I'll tell you what fills my heart with the greatest pleasure: the mental picture of all those people who hardly know me, only briefly get to know Pump Aid's workers, and who don't know you Times readers at all — but whose lives are changed by the help you have pledged.

I think of the girls at Matimura school, who now have a school loo with privacy and hygiene; of beautiful Miriam, the quietly proud chair of the Kalichero well committee; of the special show of singing and dancing in the headlights of our truck put on by the people of Mwachilolo to celebrate clean latrines and clean water; and of the little boy with ragged trousers in the village of Paulo, his water bottle his only possession. They don't take The Times, these people. They will never read this. They don't know you. And it doesn't matter.