Another long-suffering sigh from Hopwood. ‘They employ hundreds of people, and most are based at head office. Some aren’t. I’m not. I make a very specific kind of wire for them – I have a lab in my garden where I’ve worked since I set up as a sole trader, and they’re fine with that. I don’t like busy, noisy environments. One of my conditions when I started working for them was still being able to work in my own lab. If you know Gaby and Tim so well, why don’t you check all this with them?’

Gibbs nearly laughed. Gaby Struthers – as he still thought of her – was the kind of person who’d dish out fake alibis to loyal members of staff without the slightest qualm. She’d done much, much worse. Gibbs tried not to think about her role in the Francine Breary murder case; every time he did, he wanted to punch a hole in a wall.

‘So what you’re telling me is that on the dates of Billy’s first four murders, you were in your own personal laboratory making special wires, and no one will be able to verify that?’

‘Basically, frustratingly, yes.’ Hopwood offered an apologetic smile.

‘On Tuesday 6 January, when Marion was murdered, you were at the hospital with her, in her room nearly all the time.’ Gibbs stared at him. ‘You say you saw no one else in or near her room who shouldn’t have been there.’

‘I didn’t, but I fell asleep for small spells. I was exhausted. And …’

‘What, Mr Hopwood?’

‘I assume you’ve considered Kim? My sister?’

‘As a suspect, d’you mean?’

‘Well, just … in the same way you’re considering me.’ Pink spots had appeared on Hopwood’s cheeks. ‘If you think three hundred grand give-or-take is a viable motive, how about no three hundred grand? How about lack of inheritance?’

‘Marion left everything to you and cut Kim out.’ Gibbs made a note. Hopwood was right: brother and sister both had a motive. Opposite motives, equally strong. ‘Well, it’s kind of you to be willing to divide it equally between you.’

‘What? I never said … I’m not willing. I mean—’

‘You seem upset, Mr Hopwood.’

‘Did Kim tell you I’d promised her half the money?’

‘No, she didn’t. You misunderstood me. I wasn’t talking about your three hundred grand, give or take. Well, take, anyway,’ Gibbs amended. ‘When I said it was kind of you to divide it equally I didn’t mean Marion’s money. I meant suspicion of murder. That, you’re willing to share with your sister. Aren’t you?’