‘Tell him if it’s not one of his he can fuck off,’ said Seawoll.

‘Do you have an interest in this?’ asked Guleed.

‘There may be some related issues,’ I said, which was sort of true given that Tyburn’s daughter was involved. I heard Guleed pass this on and some grumbled swearing from Seawoll.

‘Tell him to get his arse down here pronto,’ he said.

‘He wants you to come in,’ said Guleed and gave me the address.

Before I left I switched off my phone and stepped out the back into the garden. The rain had eased to a misty drizzle that quickly beaded my hair and the leather of my jacket. Beverley’s garden is vast by London standards, running fifty metres down to the bank of the river, and twice as wide as her neighbours’. Despite the light pollution sullenly reflected off the low cloud, I decided not to risk tripping over the random bits of garden furniture I knew littered the overgrown lawn and conjured a werelight to show me the way.

Beverley Brook rises in Worcester Park in southeast London and flows through a ridiculous number of other parks, recreation grounds and golf courses before joining her mother at Barn Elms. She says that while she averages half a cubic metre of water per second, she’s had it up to six cubic metres per second a couple of times. And unless she gets some more care, attention and the occasional bottle of Junipero Gin, she’s not going to be responsible for where that surplus water’s going to end up.

Not a threat, you understand. But it’s wise not to take a river for granted – trust me on this.

At the end of Beverley’s garden is a bank fringed with young alder and ash striplings that drops down to the river. For most of its length Beverley Brook is shallow enough that you can clearly see the stones at the bottom, but here there was a deep pool overshadowed by a weeping willow. The surface was dark and coldly reflected my milky blue werelight as it bobbed around me in a slow orbit.

‘Hey, Bev,’ I called. ‘You in there?’

For all I knew she was kilometres away visiting her mum’s place in Wapping. Or patrolling the Thames for waifs and suicides, or whatever else it was she and her sisters spend their time searching for.

But she’s been known to surface when I’ve called her name, and once she leapt like a salmon, naked and glistening, into my arms – so it’s always worth a try.

This time there was no response. Just the drizzle and the grumble of the Kingston Bypass on the other side of the river. I waited about a minute, just so I could claim I’d waited five, and then headed back-up the garden.