‘Strange as in the way he worked the case at times. Nothing solid I could pin down, but you just get a feeling when something’s not right, you know? My guy says he saw him twice with Bolton. I showed him a pic and he ID’d Mike. Next time I saw Mike I asked him a question about the last time he interviewed Bolton, and he started telling me about when we’d questioned him about an assault. Not enough evidence for it to bring him in and charge him, of course, but Mike swore blind that was the last time he’d spoken to him.’

‘And you think what, then? That they killed him because they thought he was playing them? Double-crossing them?’

Anderson just shrugged. ‘No idea, and I could be way off the mark here. I’ve not even told Jon, it’s that tenuous. But yeah, maybe following them to that building was no accident. Maybe that was their plan all along. Maybe they’d had a falling-out, or maybe Mike had a crisis of conscience, who knows? Either way, that could explain why they killed him, but didn’t finish the job on Simmons.’

As much as Porter wanted to discount the possibility of one of their own turning on them out of hand, the objective part of his brain kicked in. It would explain why they’d known about Carter’s mic, why they were opening their doors for inspection now. They would have moved everything that Gibson knew about in case he was double-crossing them. How compromised might they still be now that Mike was dead and not feeding them any more information?

‘We have to take this to Campbell,’ he said finally.

‘And say what? We have an anonymous tip one of our team was dirty, but absolutely nothing to back it up, a copper who, by the way, we’ve given the all-singing, all-dancing funeral to for dying in the line of duty. I’m sure that’ll get me in his not-so-good graces alongside you. No bloody thank you.’

Porter chewed on his bottom lip. He knew Anderson was right, but it was the proverbial rock and hard place. If he told Campbell, there was a good chance it would be dismissed out of hand, with no supporting evidence and the alleged conspirator dead. If he didn’t, and it came out later in the investigation that it was true, it could hurt them. Correction, he thought, it could hurt him. By then there was a good chance Anderson would be sitting somewhere sunny collecting his pension.

‘I don’t know,’ he said finally. ‘Let me think about it. Who’s your guy, the one who pointed the finger at Mike?’

Anderson shook his head. ‘I promised I’d keep his name out of it unless we needed him to testify, and Mike’s not getting arrested any time soon.’