“That is the son,” said Mma Makutsi, lowering her voice, although nobody could possibly hear them. “He has a scholarship to Thornhill School. He is a bright boy, with very good handwriting.”

The uncle looked interested.

“Should I write this down?” he asked. “I could keep a record of what happens.”

Mma Makutsi was about to explain that this would not be necessary, but she changed her mind. It would give him something to do, and there was no harm in it. So the uncle wrote on a scrap of paper that he had extracted from his pocket: “Badule boy leaves house at 7 A.M. and proceeds to school on foot.”

He showed her his note, and she nodded.

“You would make a very good detective, Uncle,” she said, adding: “It is a pity you are too old.”

Twenty minutes later, Mr Badule emerged from the house and walked over to the butchery. He unlocked the door and admitted his two assistants, who had been waiting for him under a tree. A few minutes later, one of the assistants, now wearing a heavily bloodstained apron, came out carrying a large stainless steel tray, which he washed under a standpipe at the side of the building. Then two customers arrived, one having walked up the street, another getting off a minibus which stopped just beyond the take-out stall.

“Customers enter shop,” wrote the uncle. “Then leave, carrying parcels. Probably meat.”

Again he showed the note to his niece, who nodded approvingly.

“Very good. Very useful. But it is the lady we are interested in,” she said. “Soon it will be time for her to do something.”

They waited a further four hours. Then, shortly before twelve, when the car had become stiflingly hot under the sun, and just at the point when Mma Makutsi was becoming irritated by her uncle’s constant note-taking, they saw Mma Badule emerge from behind the house and walk over to the garage. There she got into the battered Mercedes-Benz and reversed out of the front drive. This was the signal for the uncle to start his car and, at a respectful distance, follow the Mercedes as it made its way into town.

Mma Badule drove fast, and it was difficult for the uncle to keep up with her in his old Austin, but they still had her in sight by the time that she drew into the driveway of a large house on Nyerere Drive. They drove past slowly, and caught a glimpse of her getting out of the car and striding towards the shady verandah. Then the luxuriant garden growth, so much richer than the miserable pawpaw trees at the butchery house, obscured their view.

But it was enough. They drove slowly round the corner and parked under a jacaranda tree at the side of the road.

“What now?” asked the uncle. “Do we wait here until she leaves?”