Mr J.L.B. Matekoni was silent. Then: “Diamonds are rather expensive, aren’t they?”

“Very expensive,” said one of the housemothers. “One thousand pula for a tiny, tiny diamond.”

“More than that,” said Mr Potokwane. “Some diamonds cost two hundred thousand pula. Just one diamond.”

Mr J.L.B. Matekoni looked despondent. He was not a mean man, and was as generous with presents as he was with his time, but he was against any waste of money and it seemed to him that to spend that much on a diamond, even for a special occasion, was entirely wasteful.

“I shall speak to Mma Ramotswe about it,” he said firmly, to bring the awkward topic to a close. “Perhaps she does not believe in diamonds.”

“No,” said Mma Potokwane. “She will believe in diamonds. All ladies believe in diamonds. That is one thing on which all ladies agree.”

MR J.L.B. Matekoni crouched down and looked at the pump. After he had finished tea with Mma Potokwane, he had followed the path that led to the pump-house. It was one of those peculiar paths that seemed to wander, but which eventually reached its destination. This path made a lazy loop round some pumpkin fields before it dipped through a donga, a deep eroded ditch, and ended up in front of the small lean-to that protected the pump. The pump-house was itself shaded by a stand of umbrella-like thorn trees, which, when Mr J.L.B. Matekoni arrived, provided a welcome circle of shade. A tin-roofed shack, like the pump-house was, could become impossibly hot in the direct rays of the sun and that would not help any machinery inside.

Mr J.L.B. Matekoni put down his tool box at the entrance to the pump-house and cautiously pushed the door open. He was careful about places like this because they were very well suited for snakes. Snakes seemed to like machinery, for some reason, and he had more than once discovered a somnolent snake curled around a part of some machine on which he was working. Why they did it, he had no idea; it might have been something to do with warmth and motion. Did snakes dream about some good place for snakes? Did they think that there was a heaven for snakes somewhere, where everything was down at ground level and there was nobody to tread on them?

His eyes took a few moments to accustom themselves to the dark of the interior, but after a while he saw that there was nothing untoward inside. The pump was driven by a large flywheel which was powered by an antiquated diesel engine. Mr J.L.B. Matekoni sighed. This was the trouble. Old diesel engines were generally reliable, but there came a point in their existence when they simply had to be pensioned off. He had hinted at this to Mma Potokwane, but she had always come up with reasons why money should be spent on other, more pressing projects.

“But water is the most important thing of all,” said Mr J.L.B. Matekoni. “If you can’t water your vegetables, then what are the children going to eat?”