‘He’s killing pairs of best friends, yes, but they’re friends with each other,’ said Wing, eye-rolling again, ‘not with him. To call him Billy Dead Mates implies he’s killing his own friends. And we’ve no reason to think he is. The opposite. There’s been no connection found between the two pairs. Linzi Birrell and Rhian Douglas existed in a very different world to the one Angela McCabe and Joshua Norbury inhabited. We’ve found nothing to suggest any overlap—’

‘They were all murdered by the same person,’ Proust interrupted flatly. ‘I call that overlap.’

‘I was going to say “nothing to suggest any overlap in their friendship circles. We’re as sure as we can be that Linzi and Rhian had no friends or acquaintances in common with Angela and Joshua. So it’s not Billy’s mates who are dead, is it?’ Wing sat back and folded his arms.

‘Aren’t you being too …?’ Sam Kombothekra began hesitantly. ‘I mean, if you think of it as “Billy of the Dead Mates”…’

‘Like Tess of the D’Urbervilles.’ Kerensa Moore smiled.

‘Why does this matter?’ Proust had adjusted his voice to its coldest setting. When alone with his team – Simon, Sam, Colin Sellers and Chris Gibbs – this tone would guarantee silent compliance for the foreseeable future, unless Simon was feeling particularly bloody-minded.

Kerensa Moore stared down at her feet and frowned, no doubt deciding not to do anything as rash as make a harmless remark ever again.

James Wing, by contrast, appeared impervious. ‘No.’ He directed his reply to Sam, bypassing Proust who sat between them. ‘Billy Of The Dead Mates That Aren’t His doesn’t work. Everyone who knows the saying behind the name knows it’s Billy No Mates as in Billy has no mates. When you change the phrase slightly, the silent reference remains: leading people to assume … rather, misleading them into assuming that it’s Billy’s mates that are dead – that he’s killed his own friends. Billy has dead mates. Can’t you see the problem?’

‘I’m looking at him right now.’ Proust stared at Wing.

‘I think DC Wing’s got a point,’ Simon forced himself to say.

‘I’m not sure most people are that literal-minded,’ Kerensa Moore said with a nervous glance at Proust. ‘Hardly anyone would get as far in their thought process as “Billy of the”, “Billy has”, etcetera.’

‘Maybe so, but it’s not ideal that we’re calling him by a name that misrepresents him,’ said Wing.

‘I take your point, but I just don’t see that it does,’ said Sam.

‘Then you don’t take his point, Sergeant,’ offered the Snowman. ‘You reject his point.’

‘No, I can see what he’s saying, completely, but the name works for me. At the most basic level …’ Sam shrugged. ‘He’s killing pairs of best friends and we’re calling him Billy Dead Mates.’