Mma Ramotswe interrupted her with a laugh. “Anybody can invent something, Mma. Even you and I—we might invent something. You do not have to be a scientist to invent something very important. Some inventions just happen. Penicillin. You know about that?”

Mma Makutsi saw the conversation drifting away from teapots. “I was wondering …”

“We were taught about penicillin in school,” Mma Ramotswe mused. “At Mochudi. We were taught about the man who found penicillin growing in …” She tailed off. Again, it was hard to remember, even if she could see herself quite clearly in the school on the top of the kopje overlooking Mochudi, with the morning sun coming through the window, illuminating in its shafts of light the little flecks of floating dust; and the voice of the teacher telling them about the great inventions that had changed the world. Everything, all these great things, had happened so far away—or so it seemed to her at the time. The world was made to sound as if it belonged to other people—to those who lived in distant countries that were so different from Botswana; that was before people had learned to assert that the world was theirs too, that what happened in Botswana was every bit as important, and valuable, as what happened anywhere else.

But where had that doctor grown the penicillin that was to save so many lives? In his garden? She thought not. It was in his laboratory somewhere, perhaps in a cup of tea that he left on a windowsill, as Mr. J.L.B. Matekoni had done once and Mma Ramotswe had discovered it, months later, when the half-finished liquid had turned to green mould.

“In a cup of tea,” she said hesitantly. “Maybe. Or in a saucer, perhaps.”

“That is very interesting, Mma,” said Mma Makutsi briskly. “But I have been thinking about a more efficient way of making the tea in this office. I am not interested in making penicillin or inventing anything.”

Mma Ramotswe nodded encouragingly. “It is a good thing to be efficient,” she said.

Mma Makutsi seized her chance. “So why don’t we use the big teapot to make the ordinary tea,” she said. “There are always more people wanting ordinary tea—Mr. Polopetsi, for instance, and Charlie and Fanwell. If we made the ordinary tea in that big pot, then I would not have to make a second pot.” She paused. “And it would make no difference to your red bush tea, Mma. You would still have more than enough.”