‘How many more of these posh young ladies are you planning to bring in?’ she asked. ‘Or are we going to have start sending out to Fortnum and Masons for refs?’

‘This one has to go in a Falcon cell,’ I said, which wiped the smile off her face.

The same wartime manual with the prisoner management rules also contained instructions for creating cells for magical POWs. Nightingale decided that it would be an interesting way to combine training and necessity if we were to enchant the ‘wards’ together. These proved to be strips of iron inlaid with a crude copper filigree in loops and whirls. You enchant them as you beat them into shape – it’s very therapeutic and good for your upper body strength. We selected two cells in Belgravia’s custody suite and fused the strips across the front of the doors and then painted them over with institutional blue paint. Nightingale did the fusing and I did the painting.

I then spent a fun afternoon locked in one of the cells trying to magic my way out – followed by an unpleasant evening when I realised that I’d been abandoned by Nightingale, who’d put the fix in with the custody sergeant. I had just resigned myself to a night in the cells and was wondering what time refs were up when Guleed took pity on me and let me out.

When the custody sergeant asked for a name I expected our suspect to refuse but to my surprise she gave the sergeant a cheerful smile and said – ‘Lady Caroline Elizabeth Louise Linden-Limmer’. She turned that smile on me and Guleed. ‘Mum’s a viscountess.’

‘Very nice,’ said the custody sergeant. ‘And mine’s a Jaffa Cake.’

Thirty seconds looking for Caroline’s mother on Google led to the Lady Helena Louise Linden-Limmer, or rather to a famous picture of her wearing nothing but a leopard skin fur coat taken by David Bailey in 1964. After that in the listing came her autobiography, Growing up Wild: A Childhood in Africa, and a scanned article from the Observer Colour Supplement circa 1988 about her menagerie – as she called it – of adopted and fostered kids. There had been six at that point. All girls. I looked at the photographs. Two were black, one was brown, one was possibly Chinese or South East Asian. Of the white girls one had cerebral palsy and other had been a victim of thalidomide. According to the article, Lady Linden-Limmer had run a health clinic in Goa and then in Calcutta, and had worked with people suffering from leprosy.

You can’t just return home and stop caring, she told the interviewer.

One of the black girls in the photographs was about four, wearing a grubby blue smock and a sly expression that was an echo of the woman we had in the cells – Caroline, I presumed.