Zach brought his two plates to the table and, after a brief introduction to Nightingale, began to plough through the heaps of food. To eat as much as he did and stay skinny he must burn calories like a racehorse. Was it a fairy thing or within the normal range of human metabolism? I wondered if I could persuade Zach to spend a day being tested by Dr Walid. I was willing to bet he’d never had a demi-fae to experiment on. It would be nice to know whether there was a demonstrable genetic difference, but Dr Walid said that normal human variations were wide enough that you’d need samples from hundreds of subjects to establish that. Thousands if you wanted a statistically significant answer.

Low sample size – one of the reasons why magic and science are hard to reconcile.

Zach kept his attention on his food while I told Nightingale about James Gallagher’s visit to Powis Square and the vestigium I’d sensed there.

‘Sounds like a floating market,’ said Nightingale.

‘A nazareth?’ I asked.

‘Like a nazareth only for those that live in our world, rather than your average criminal,’ said Nightingale. ‘We used to call them goblin markets.’ He turned to Zach. ‘Do you know where it is?’

‘Not me, guv,’ said Zach. ‘I’m strictly persona non grata amongst them kind of people.’

‘Could you find it, though?’

‘Maybe,’ said Zach. ‘What’s it worth?’

Nightingale leaned forward and, whip-fast, grabbed Zach’s wrist and twisted it palm up so that Zach had to half rise out of his chair to avoid breaking it.

‘You’re in my house, Zachary Palmer, eating at my table, and I don’t care how modern you think you are, I know you know that’s an obligation you can’t avoid.’ He smiled and released Zach’s wrist. ‘I’m not asking you to put yourself at risk, just find us the current location. We’ll do the rest.’

‘You only had to ask,’ said Zach.

‘Can you find it by this afternoon?’ asked Nightingale.

‘Course,’ he said. ‘But I’m going to need some readies – for transport, washing some hands, that sort of thing.’

‘How much?’

‘Pony,’ said Zach, meaning £500.

Nightingale pulled a silver money clip from his jacket pocket and peeled off five fifties and handed them to Zach, who disappeared them so fast I didn’t see where they went. He didn’t protest the shortfall, either.

‘Let’s take our coffee to the library,’ said Nightingale.

‘Will you be all right here?’ I asked.

‘Don’t worry about me,’ said Zach who was already eyeing up the salvers for a return visit.

‘One does rather wonder if he will stop before he explodes,’ said Nightingale as we walked along the balcony.

‘It’s one of those paradox thingies,’ I said. ‘What happens when the unstoppable cook meets the unfillable stomach?’