I tried to make myself like Judy and be nice to her. My efforts must have worked, for she seemed happy to come with me to take her passport photographs at 4E. We all walked together to the end of Russia Road, where Silver left us to get the bus to Swiss Cottage. Judy watched him go, rather wistfully, I thought, and said with some nervousness that I didn’t expect her to climb on roofs, did I? We’d let ourselves in at the front door, I said. Andrew had given me a key. It was then that we had an unlooked-for piece of luck.

At first it seemed like disaster or near-disaster. We were on the doorstep of 4 Torrington Gardens, Judy with camera, tripod, and a bagful of photographic stuff. I was fishing the key out of my pocket when the door was opened by Sean Francis. We took a step back. He looked at me, half-recognizing me as the Nylands’ houseplant minder, then at Judy. An uncertain smile hovered, he put his head on one side, said, “Hello. I know you, don’t I? Can’t remember where from.”

“Norroy,” Judy said. “Norroy House. The Ghost Child.”

“That’s right. How extraordinary. How are your mum and dad? And the terribly nice lady who used to make endless cups of tea?”

“They’re fine, they’re all fine.”

“Look, are you living around here? I’m in a mad rush, I’m late before I’ve started, but give me a ring, will you? We might have a coffee or a drink or something.”

Judy said she would, she’d like to. He ran off down Torrington Gardens. Not a word had been said about me or watering the houseplants or the Nylands. We stepped inside the hall and closed the door behind us. “What was all that about?” I said. “How d’you know him?”

Her parents had lent their house to the television production company that was making a film Sean Francis was in. The company paid them a lot of money, refurnished the house and partly decorated it, and the family remained in what had been a housekeeper’s flat. Judy and her brother got to know some of the cast quite well, a state of affairs helped by their grandmother, who lived with them, luring some of the actors away from their mobile canteen and plying them with tea and cakes.

“It was just before I started going about with Silver. I told him about it but I expect he’s forgotten.”

I decided not to comment on that. We started up the marble staircase, eight flights of it. “Would you have a drink with him? You wouldn’t mind?”

“It would be a funny sort of girl who’d mind,” she said.