He looked nonplussed, thought about it and admitted that he didn’t think she’d spoken the whole time he’d been with her. After that I asked a few closing questions, but St John had been too busy bleeding to notice where his assailant had gone and he never got her name, let alone her phone number.

I told him I thought he was bearing up well, considering.

‘Right now,’ he said, ‘I’m on some really serious medication. I don’t like to think about what’s going to happen when I come off it.’

I checked with the doctors on my way out – the missing penis had never been found. Once I’d finished up my notes – this was still an official Metropolitan Police investigation – I checked in on Lesley, who was one floor up. She was still asleep, her face hidden by a swathe of bandages. I stood by her bed for a while. Dr Walid had said that I’d definitely saved her life, and possibly increased the chances of successful reconstructive surgery. I couldn’t help thinking that hanging out with me had almost killed her. It had been less than six months since she’d gone for those coffees and I’d met a ghost, and it was terrifying that that might have been all the difference there was between me being the one wearing the bandages.

Less terrifying, but much more depressing, was figuring out why it had all kicked off back on that cold January night or, more precisely, that sunny winter’s day on Hampstead Heath when Toby the dog bit Brandon Coopertown on the nose. That was the same week the Linbury Studio, the Royal Opera House’s second, smaller auditorium had staged a revival of a little-known play entitled The Married Libertine, first shown in the main theatre in 1761 and never shown again, as far as I could tell, anywhere else in the world, its author – Charles Macklin. The Royal Opera House fell over themselves to give me access to their booking records, presumably in the hope I’d then go away for ever, and I found William Skirmish and Brendan Coopertown had attended a performance on the same night. A random set of circumstances are what did for William Skirmish, and all those who were maimed or died after him – like I said – depressing.

If you want to help, Nightingale had told me, study harder, learn faster. Do the job.

I’d have stayed longer, but I was on the clock.

Nightingale, in an adjacent room, was awake and sitting up and doing the Telegraph crossword. We discussed the case of the missing penis.

‘Vagina dentata,’ said Nightingale. I wasn’t sure that I was reassured by the thought that it was common enough for there to be a technical term for it. ‘Could be oriental, something out of Chinatown,’ he said.

‘Not Japanese,’ I said. ‘The victim was quite clear about that.’