It had to be Nightingale, I realised. The counterweight, the human balance to the supernatural, and that meant that they couldn’t control him. The only thing that separated Nightingale from an ordinary guy was his magic, which meant that the magic must supply a defence. It was a stretch, but it isn’t easy thinking things through when the personification of a historic London river is mentally trying to overwhelm you.

To try and buy time I attempted to throw myself backwards. It didn’t work, but it did stop my next lurch towards the fountain. Nightingale hadn’t taught me a block to the magic yet, so I reached for Impello instead. Lining up the forma in my mind was so much easier than I expected – later I speculated that whatever it was Tyburn was doing acted on the instinctive bit of my brain, not the ‘higher’ functions – that I got carried away.

‘Impello,’ I said, and tried to lift the statue off its pedestal.

Tyburn’s eyes widened at the sound of cracking marble. She whirled to look and as her eyes left mine I staggered back, suddenly free. I felt the shape in my mind slip out of control and the statue’s head disintegrated in a spray of marble chips. I felt a blow to my shoulder and a sharp cut on my face and a chunk of marble the size of a small dog slammed into the patio tiles by my feet.

I saw that the birdbath had also cracked, and that water was escaping and spreading across the patio like a bloodstain. Tyburn turned back to look at me. There was a cut on her forehead and her sundress was torn just above her hip.

She’d gone very quiet, and that was not a good sign. I’d seen that quiet before, on my mum and on the face of a woman whose brother had just been knocked down by a drunk driver. People are conditioned by the media to think that black women are all shouting and head-shaking and girlfriending and ‘oh, no you didn’t’, and if they’re not sassy then they’re dignified and downtrodden and soldiering on and ‘I don’t understand why folks just can’t get along’. But if you see a black woman go quiet the way Tyburn did, the eyes bright, the lips straight and the face still as a death mask, you have made an enemy for life: do not pass go, do not collect two hundred quid.