When I paused to check the tyres – it’s a police thing – I saw that they’d all but rotted away and that the van had been there long enough for the roots of a young tree to tangle itself in the wheel arch. From the other side of the van I could hear a woman humming to herself. And I could smell, appropriately given the vehicle, that someone was smoking a spliff. I smiled. Because it’s always a comfort when you’re the police to walk into a situation knowing that if all else fails you can still make a legitimate arrest.

The humming stopped.

‘We don’t drive it around much these days,’ said a woman from the other side of the van. ‘You can’t get the wheels anymore, or so I’m told.’ I recognised the voice from the phone call – it was Miss Teveyddyadd. Or more properly, as five seconds on Google had revealed, Miss Tefeidiad. Or even more precisely, since we were on the English side of the border, the goddess of the River Teme. Nightingale calls them Genius Loci, spirits of a locality, and says that the first rule of dealing with them in person is to remember that every single one of them is different.

‘They are, after all,’ he’d said, and smiled, ‘spirits of a specific locality. It’s only logical that they will be somewhat variable.’

Miss Tefeidiad was as tall as I was, with a shaggy head of blonde hair with a grey streak over her temple, a long straight nose, thin lips and black eyes. It was the sort of face that had become attractively interesting around puberty and was going to stay that way until the owner was carried out of their nursing home feet first. She appeared to be in her well-preserved mid-sixties, but I’d learnt not to trust appearances.

She stood waiting for me on the far side of the VW, where a heavy red and gold awning was attached above the open side doors and stretched out on a pair of poles. In its shade was an old wooden kitchen table covered in a red and white check vinyl table cloth.

‘You must be the famous Peter Grant,’ she said, and ushered me into one of four grey metal folding chairs set around the table. Another of the chairs was occupied by a handsome middle-aged white woman with long brown hair, hazel eyes and the same long straight nose as her – sister? mother? Relative, certainly. She wore an orange sun dress and broad-brimmed straw hat.

‘This is my daughter Corve,’ said Miss Tefeidiad.

Corve reached out and shook my hand. Her grip was firm and the skin rough from hard work.

‘Delighted to meet you, Peter.’ Her Welsh accent was less pronounced than her mother’s. I noticed that there was no visible sign of the spliff.