‘No,’ said Dr Vaughan slowly. ‘It is not an aneurysm because an aneurysm is caused by a weakening in a blood vessel which distends over time and then, if one is unlucky, ruptures causing an intracranial bleed. Which as we know is not very good for the brain, is it?’

‘But that’s intracranial bleeding,’ I said. ‘I’ve seen slides like this before.’

‘That may be so, but it is not caused by an aneurysm,’ she said and Guleed gave me a pitying look.

Guleed always knew how to keep her mouth shut, and had this mad way of just fading into the background whenever she wanted to. Well, we all have our ways of dealing with difficulties – mine is to ask stupid questions.

‘It’s not natural causes, though,’ I said. ‘Is it?’

‘Well,’ said Dr Vaughan, ‘here’s the thing. If you look at this close-up here – see where the brain looks spongy? These are indications of tiny points of tissue damage to the brain.’

‘Caused by what?’ I asked.

Dr Walid chuckled and Dr Vaughan sighed.

‘To be honest, my guess would be that somebody sliced open her brain, pricked it with narrow bore needles and then reassembled the brain – seamlessly mind you – and then popped it back in her head with her none the wiser.’

‘That seems an unlikely scenario,’ I said.

‘It does, doesn’t it,’ said Dr Vaughan. ‘In any case, one of these pinpricks also jabbed a blood vessel, which led to the intracranial bleeding, which was the ultimate cause of death.’

I asked what caused the pinpricks, if not narrow bore needles, and Dr Vaughan gave me a sunny smile.

‘As you know, I’ve been reviewing Dr Walid’s casework,’ she said. ‘And reviewing the “literature” he’s supplied on related subjects. Now, to be fair to the colleagues that came before us, these gentlemen didn’t have access to modern imaging techniques, but even so they can be remarkably vague as to the distinction between cerebrovascular and physical trauma. However, they did leave some excellent specimens behind.’

A room full of them, I knew, some of them dating back to the eighteenth century. Apparently it was good form in the old days for a wizard to leave his body to the Folly along with his notebooks, unreturned library books and any spare valuables he had lying around – cash, antiques, good quality arable land in the Midlands or home counties. It was the land bequests that underpinned the charitable fund that was paying Dr Vaughan’s salary.

‘You’d better not tell the Hunterian you’ve got these,’ Dr Vaughan had said when she was introduced to the Folly’s collection. ‘Or they’d be down here backing up a lorry to your front door and no mistake.’