‘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?’

‘Oh!’ Sam looked pleased to be chosen. ‘Well, if it was someone I knew well, I might say, “Aren’t you going to take off your gloves?” in a light-hearted way. I wouldn’t want to upset them or make them feel awkward.’

‘Sergeant Kombothekra would find his own woolliest gloves and put them on, lest his guest should feel alone and misunderstood,’ Proust told Moore.

‘But if it was someone I wasn’t close to – and there are plenty I trust in that category – I wouldn’t say anything. I’d just think, “That’s unusual” – but people are, aren’t they?’

‘Right.’ Kerensa Moore nodded. ‘The very answer I wanted. I think we can assume, in the absence of evidence to the contrary, that Billy figured he could keep his gloves on and no one was likely to query it because of basic politeness.’ No one disagreed with this.

‘He wore gloves, but left DNA from his mouth on the crockery,’ said Proust. ‘Is he a moron?’

‘I’d say not,’ said Moore. ‘I think the gloves might have been as much about avoiding skin contact with the gun as anything else. Symbolic distance from the act.’

‘I’m done with Linzi Birrell,’ said Dunning. ‘Who wants to take Angela McCabe?’

‘I will,’ said Simon. ‘Angela McCabe, forty-seven years old, address 7 Bradby Avenue, Chiswick. Happily married, two children, ten and eight. Killed 11 November 2014. And with his third murder, Billy moves to a different socio-economic bracket. Angela McCabe was upper middle class and so was Joshua Norbury, whereas Linzi Birrell and Rhian Douglas both came from working-class backgrounds and led working-class lives. Angela and Josh had been best friends – like particularly close siblings, we’re told – for nearly fifteen years, since they met on a …’ – Simon cleared his throat – ‘… holistic holiday in Crete, where they were on the same creative writing course.’