‘You mean, why haven’t I given it to the drug companies?’ asked Lady Helena. ‘Because it’s difficult, dangerous to the witch, and has a one-in-twenty success rate. I’d used it in extremis and tried to refine it, but the most common result is a type of terrible half-life.’

‘Zombies,’ said Caroline, which got her a glare from her mother. ‘What? I’m just saying – zombies. That’s what you get when it goes wrong.’

‘I decided I couldn’t trust anyone with the technique,’ said Lady Helena. ‘Least of all the medical establishment. God, can you imagine what the military might do with it? It doesn’t bear thinking about.’

It was after her encounter with Larry the Lark that she concluded the medical knowledge she’d developed was too dangerous to be passed on.

‘I’ve decided that it has to die with me,’ she said.

‘What about Albert?’ asked Nightingale.

‘Quite,’ she said. ‘What about dear old Albert?’

She’d arranged to meet him at her hotel, but he must have heard that she’d visited the club because he turned up ready to fight.

‘It was a sort of mutual ambush,’ said Lady Caroline. ‘He had first go, but I always was faster than him. Things got rather disagreeable and I’m afraid the hotel rather bore the brunt of it. So it’s just as well I always stayed under an assumed name.’

‘Was this the Pontypool Hotel on Argyle Square?’ asked Nightingale.

‘As a matter of fact it was,’ said Lady Helena.

‘I was called in to investigate that,’ said Nightingale. And, to me, ‘They thought it was a gas explosion at first, then arson and then the IRA. Only once they’d exhausted those possibilities did they think of me, and the trail had grown somewhat cold by then.’ He looked at Lady Helena again. ‘Thank you for clearing that up.’

Not to mention thank you for adding attempted murder, gross negligence and identity fraud to your charge list, I thought, or explaining your cheerfully relaxed attitude to medical ethics.

‘You do understand what happens when you overuse magic?’ she asked.

‘We call it hyperthaumaturgical degradation,’ said Nightingale.

Lady Helena nodded.

‘Useful term,’ she said. ‘That’s what happened to dear Albert. Which I thought a fitting punishment. I didn’t have time for a coup de grace – the police were practically knocking on what was left of the front door when I made myself scarce.’

Nightingale nodded thoughtfully in a way that made me think that somebody was going to be digging out incident reports from 1979, and just for a change it wasn’t going to be me. There was a good chance it would be a big box full of papers – which would suit Nightingale much better anyway.

Without Albert, the charity funding evaporated and, in any case, she’d begun to have doubts about the ethics of her work.

‘But you must have saved lives,’ I said.