Mma Ramotswe looked up from her desk. She smiled. “Thinking? We all have a lot to think about, I suppose.”

Mma Makutsi busied herself with the kettle. “Yes, Mma. You know how sometimes a good idea comes to you? You don’t necessarily think about it deliberately, but it just comes. And there you have your idea.”

“Yes,” said Mma Ramotswe. “And what idea do you have, Mma Makutsi? I’m sure it will be a good one.” She was always polite-and encouraging too; a lesser employer might have said, Thinking? There is work to do, Mma! Or, even more discouragingly, I am the one to do the thinking round here, Mma!

Mma Makutsi glanced at Mma Ramotswe. There was no trace of sarcasm in her voice; Mma Ramotswe did not believe in sarcasm. “This idea is about teapots. About efficiency and teapots. Yes, it’s about those two things.”

“Good,” said Mma Ramotswe. “Anybody who could invent a more efficient teapot would be doing a great service to…” She paused, before concluding: “to all tea-drinking people.”

Mma Makutsi swallowed; sometimes it was easier to deal with a hostile reaction rather than a welcoming one. “Well, I don’t think I could invent a new teapot, Mma. I am not that sort of person. But-”

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.