‘Let me rephrase that and talk slowly,’ said Dr Walid. ‘There’s no such thing as a safe tranquilliser dart.’

‘It doesn’t have to be a dart,’ I said. ‘Every minute we leave Lesley sequestrated there’s a chance that Henry Pyke’s going to make her face fall off. To do magic your mind has to be working. Shut down the conscious bit of the brain, and I’m willing to bet Henry can’t do his spell and Lesley’s face stays the way God intended.’

I could see from Dr Walid’s expression that he thought I was right. ‘But what then?’ he asked. ‘We can’t keep her in a medical coma indefinitely.’

‘We buy time,’ I said. ‘For Nightingale to wake up, for me to get back to the Folly library, for Henry Pyke to die of old age … or whatever it is undead people do when they go.’

Dr Walid went grumbling off and came back a bit later with two disposable syrettes in sterile packaging with a biohazard label and a sticker that said ‘Keep out of the hands of children’.

‘Etorphine hydrochloride in solution,’ he said. ‘Enough to sedate a human female in the sixty-five kilogram weight range.’

‘Is it fast?’ I asked.

‘It’s what they use to trank rhinos,’ he said, and handed me a second package with another two syrettes. ‘This is the reversing agent, narcan. If you stick yourself with the etorphine, then you use this straight away before you call an ambulance, and try to make sure the paramedics get this card.’

He handed me a card that was still warm from the lamination machine. In Dr Walid’s neat, capitalised handwriting it said: ‘Warning. I have been stupid enough to stick myself with etorphine hydrochloride’, and listed the procedures the paramedics were to follow. Most of them concerned resuscitation and heroic measures to maintain heartbeat and respiration.

I patted my jacket nervously as I rode the lift down to the reception area, and repeated under my breath that the tranquillisers were in the left-hand pocket and the reversing agent on the right.

Beverley was waiting for me in the No Waiting zone dressed in khaki cargo pants and a cropped black t-shirt with WINE BACK HERE stencilled across her breasts.

‘Ta-da!’ she said, and showed me her car. It was a canary-yellow BMW Mini convertible, the Cooper S model with the supercharger at the back and the run-flat tires. It was about as a conspicuous a car as you can drive in central London and still fit into a standard parking space. I was happy to let her drive – I’ve still got some standards.