‘Cling film, indeed,’ William muttered, counting out the dice. Priest outnumbered him three to one this time. ‘How fascinating. A very personal way to kill someone, don’t you think? Like strangulation. You have to really hate your victim to strangle them, you know. Same with cling film – you just have to accept that they’ll be thrashing around in your arms for three or four minutes, maybe longer with someone of greater stamina. Although I find that physical stamina is less important than a person’s desire to live.’

Find. As in present tense. Not ready for parole yet, old chum. Not that you’ll ever be eligible for it.

‘Have you ever tried it?’ Priest asked. The brothers tapped their fists together in a tradition that dated back to their childhood and rolled. William talked almost absent-mindedly as he moved the dice around.

‘No. I did once design a contraption that latched around a man’s neck like a dog collar and could be expanded by means of a rubber ring and pump concealed in the frame. It could be operated remotely, by an electronic signal transmitted from a device I had stitched into my trousers.’

‘Did you ever have the opportunity to test this contrivance of yours?’

Priest watched, vexed, as William tipped over his units with his finger as each dice cast in turn went in the older brother’s favour.

‘I regret not. Pity, too. I had a fine-looking Fleet Street banker in mind as a guinea pig.’

Behind William, the nervous-looking warden shuffled his feet and coughed again. Priest looked up sharply and whatever it was that the warden was about to say evaporated in his throat. He looked young, barely out of school. Priest didn’t recognise him – presumably then he was new and ill-used to a serial killer’s musings.

‘Well,’ Priest began as he checked through what cards he had left, ‘sorry to disappoint but the first victim had a needle mark and no defensive wounds.’

‘Oh, how boring. That’s like microwaving a roast dinner. But, in the absence of a physical confrontation, the killer could be either male or female, don’t you think?’ William cast him a knowing look, although Priest had already considered the point. ‘Were there any mementos taken? Underwear, fingers, an eyeball, perhaps?’

‘Afraid not. But the second victim had her face mutilated.’

‘Oh?’ expressed William, interested. He reached across and passed Priest the dice and they rolled again. The novice warden shifted his weight uncomfortably, watching all the time and occasionally glancing at the CCTV flashing above them. Fat lot of good he would be if Wills kicks off. ‘No doubt the killer left the first victim alone, other than the grievous act of killing itself, of course?’

‘That’s right.’