They headed back to their cars to split up and work through the remainder of the list, leaving Sandford and Clarkson to watch Bolton’s car. Porter thought back to Gibson’s funeral. The conversation with Anderson. The grass who gave up Mike’s name, however unsubstantiated. First Carter’s wire, and now this? If there was someone else on the inside, then he or she would keep the lowest of profiles after everything that had happened. It would be hard enough to track Bolton down without their every move being compromised. A man with Bolton’s connections and money could hide for months – years, even – without that kind of help.

Porter felt the onset of a headache and rubbed at his temple. The day had started with so much promise, and now things were grinding to a halt again, derailed by an unseen adversary. He could only fight against what was in front of him. There had to be a way to draw his opponents out.

They were half a mile away from the station after a fruitless afternoon when it came to him, and he smiled.

Porter took the stairs two at a time in an effort to catch up. He reached the landing just as the door to the main office drifted closed, but he could see Anderson on the other side, and yanked it open.

‘Anderson, you got a second?’

Anderson turned and shrugged. ‘Yeah, what’s up?’

‘Out here?’ Porter gestured towards the corridor behind him.

Anderson followed him out and stood, arms folded, resting on top of his gut. Porter wondered if he could rest a pint glass on it the same way.

‘What’s up?’

Porter looked both ways and leant in, the universal gesture of just between you and me. ‘That guy you mentioned, the one you told me about at the funeral. Can you talk to him again? I think we need his help. There’s no other way Bolton could have known we were coming.’

‘What, you still think they’ve got another one in their pocket?’

Porter shrugged. ‘You got a better theory as to how he got out of there before we showed up?’

Anderson stared blankly back at him. ‘Maybe we’re chasing shadows. Maybe there’s no big conspiracy and he just got lucky.’

‘Yeah, maybe, but that’s more maybes than I’m comfortable with. What’s your guy’s name? I want to see if he’ll talk to me about Mike. Maybe there’s something else he heard, something he doesn’t think matters, anything that might help us.’

Anderson shook his head. ‘I gave him my word I’d keep him out of it unless we need him on the record.’