‘We sit tight.’ Gibson looked around. ‘Get the others to pull into the alley over there in case they come out fast and head back our way. Move ours as well. I’ll keep an eye.’

Simmons did as she was told, and a minute later the street was deserted again. She told the other officers to wait in their vehicles with the key in the ignition in case they needed to pursue, and she went back to where Gibson stood glued to the wall.

‘Any sign?’

‘Nothing. Swap with me a second while I check in with Bravo.’

He peeled away from the wall and she peered around the edge once more as he whispered into his phone. The doorway was around a hundred and fifty feet away, and the dark blue door looked firmly shut. She looked up at the storeys above it. Each of the other three floors had a matching pair of large windows, turned into mirrors by the angle of the sun. No more than three minutes had elapsed since the men disappeared inside, but it felt like the longest wait of her life.

She heard the engine of the car rev up and it jerked away from the kerb, still with the solitary figure inside.

‘Car’s gone, guv. Bolton and Carter must still be inside. What do we do?’

Gibson’s answer came low and urgent over her shoulder. ‘We stay with our man, and stay on Bolton.’

What the hell are they doing in there? Is Carter still our man, or is he playing both sides?

Carter followed Bolton towards stairs. Most of the light inside came through the windows even though Bolton had flicked a series of switches when they came in. The bulbs shone feebly and left the darkness in the furthest corners unscathed. A large cargo door at the rear of the ground floor was so rusted that it could have been painted brown. Four parallel lines of workbenches sat in the centre. That must have been where they gutted and scaled the fish. Carter sniffed the air. There wasn’t even a trace of telltale fishy odour. He was pretty sure no fish had passed through that door for a good few years.

Bolton took the stairs two at a time without looking back, and Carter had to practically trot up them just to keep up. Neither of them had spoken a word since they came inside. When they reached the top of the final staircase, Bolton led him through a doorway with twisted hinges hanging from the side that had long since given up their grip on the door itself.