What happens to her is nothing like Hans Christian Andersen’s version or the Disney film. She is enchanted by the beautiful voice of a local man, drifting out of the church towards the waves. And it is the man who then goes to live with her in the kingdom of the Merpeople. She doesn’t need to give up her tail and grow legs to have a life with him on land.

Milly and I had always planned to write a book about her, with my words and her illustrations.

‘You’re my mermaid,’ Zac said, as soon as I finished the story. ‘That is what I want to do for you.’ He knew I would never want to leave Cornwall, though before he met me he’d viewed his job there as a brief stop on his starry route to someplace else. ‘We’ll stay here,’ he said, ‘in your world.’ I was moved by that. And in his debt.

That was four months ago. Since then, we’d spent just three nights apart, when he attended a medical congress in Moldova towards the end of the summer. I’d missed him during that trip, despite the fact that living with a man for the first time wasn’t entirely easy for me. My grandmother brought me up with a strange mixture of regulation that I didn’t miss and freedom that I did. I felt so visible, so watched and accountable, when before I could disappear for what seemed endless stretches of time. But none of that was Zac’s fault.

I’d come to my special place to consider all this. It was where I liked to read and think and scribble hospital stories in my secret journal, which I kept hidden from Zac. I was wearing his parka, hugging it around myself, and sipping from the thermos of coffee I brought with me. The bench that I was sitting on was erected by the town soon after my parents died. The tarnished plaque behind my back was engraved with the words, In Remembrance of Squadron Leader Edward Lawrence and His Wife, Matilda Lawrence.

The bench sat on a section of the coastal path my parents had often walked together, above a gorge in the cliff that made a kind of waterfall down to the rocks below. Usually the waterfall sounded like thunder, and the sea churned and heaved its foam. On that October day, though, the waterfall was a trickle of gentle music, and the sea was so calm I could see the rocks below its glassy surface. Already it was past the high season. There were few other walkers despite the unseasonally mild autumn morning.