“I win,” she seems to tell them both constantly, although she never utters a word.

Cory tired of art college after a few months. He appeared on the doorstep one day looking lean and tanned and healthful, as if he’d walked all the way from London, although he said he’d come by train. Diana managed to refrain from chucking him under the chin and saying, “I knew it wouldn’t last”—partly because it seemed impolitic; partly because he wasn’t alone.

“Mum?” he said, in a voice that fluctuated between terror and joy. “This is Stella Lyell.” There was no need for him to add that he thought he was in love.

“Two college dropouts together!” the girl added, which was the closest she ever came to explaining herself. Even there, on the doorstep, in the first few seconds, the imbalance was obvious: Stella only had fleeting, friendly glances for Cory, whereas he devoured her with his eyes.

Byrne Hall was the focus of her attention; she kept saying, “Oh my God, this place is so cool!”

Stella Lyell brought mess and noise in her wake; the house had never known anything like it. She hadn’t arrived with a lot of luggage, but somehow her tangled-up clothes littered every room; her music filled the house; her wild moods sucked up all the oxygen and made it difficult to breathe.

Diana had been mildly anxious about her forthcoming appointment at the Harley Street clinic—a recurring twinge is probably just a twinge, but still . . . Now she began looking forward to it, as a few days’ break from her son’s guest.

One afternoon Diana thought they’d gone down to the beach—Stella was a keen swimmer, and where Stella led, Cory followed—so she sneaked into his room to take a look at the paintings. When the twinge came on she went to the window and stood still, holding her side, waiting for it to pass. The girl was in the garden, lying on the grass in short shorts and a bikini top, but there was no sign of Cory. Diana turned round and there he was, curled on top of the bed, looking back at her with raw eyes. His cheeks were pink and wet.

“Cory! Sweetheart . . .”

Diana knelt beside him and held his limp hand. When she stroked his hair he squeezed his eyes shut, but the tears leaked out anyway. She thought he was going to tell her something terrible—she didn’t know what, only that it would be terrible—but when at last he managed to get the words out, all he said was, “She’s so mean.” He might have been fourteen again, and Diana almost smiled.

“Have you had a tiff?” she said. “Everyone has tiffs. It’ll blow over.”