There was a ripple of laughter around the room – as there had been, traditionally, whenever this particular detail had come up.

‘Linzi said, “But it’s not the same,”’ Dunning went on. ‘Miff said, “Darling, if you don’t want it, I’ll happily take it off your hands.” That’s when Linzi walked out and Miff sat down and gave a public performance of really enjoying the lasagne, for the sake of PR. Though you’d have thought not fighting with the customers might have been a more sensible approach.’

‘Ahmed said Linzi never mentioned this altercation to him,’ Simon cut in again with another detail at risk of being omitted, one that had bothered him a bit. ‘She’d been attacked unreasonably by the owner of the café across the road – why wouldn’t she tell her fiancé?’

‘Because it’s a boring-as-shite story?’ Grace Woolston suggested.

Probably. Simon made the concession silently.

‘After Linzi’s death, fingerprints were found in her flat, as they were at all the murder scenes,’ said Dunning. ‘But different unidentifiable fingerprints in each case, suggesting Billy either wore gloves or wiped away all traces of his or her presence at the crime scenes. I don’t think the latter option’s practical, personally …’

‘Me neither,’ said James Wing. ‘We’d have found a few of Billy’s prints at all four scenes, enough to tell us it was the same person. We know that anyway from the little books, but that’s circumstantial.’

‘Which means we don’t know it,’ said Simon. ‘We mustn’t ever forget that we’re assuming the same person killed all four, because of the books and the other similarities. Doesn’t make it true.’

‘Of course it’s the same killer,’ said Proust impatiently. ‘Can we please not waste time?’

‘The gloves thing bothers me,’ said Grace Woolston. ‘You’re in someone’s house chatting away, and you haven’t taken off your gloves? Wouldn’t they be suspicious?’

‘They might if they had reason to fear you,’ said Sam, ‘but the victims invited Billy into their homes, which suggests trust, not fear. In which case, you’d simply think, “Funny he – or she – hasn’t taken the gloves off.”’

‘Happens all the time,’ said Dunning. ‘Visitors come round and sit there in their coats, even when you’ve got the heating up, saying, “I’ll take it off in a sec, just let me warm up first.”’

Simon imagined that anyone visiting Dunning might keep their coat on to effect a quick getaway when things became unbearable.

‘Gloves are slightly different,’ said Proust. ‘I think DC Woolston has a point. No one walks into a heated building and leaves their gloves on.’

‘You’re all right, I think,’ said Kerensa Moore, playing the role of diplomatic parent. ‘No one does that, true – or very few people – but if someone you trusted enough to invite into your home and make tea for happened to do it, what would you do? Sergeant Kombothekra: what would you do?’