The colonel was standing with his arms folded across his greatcoat, his legs slightly apart. On hearing Luke’s request he turned towards him with his customary blank expression. ‘You are not in charge here, Mr Carlton,’ he said in English. ‘This is our investigation and you are in Moscow now.’ For several seconds they stared at each other. This was a make-or-break moment in the investigation and both men knew it. Walk out of here and Luke would return to London with mission failure, having learned absolutely nothing. Stay put, cooperate with these thugs, and he might get somewhere, while at the same time leaving his conscience in the gutter.

It was Petrov who broke the silence. He issued a command to a large man in overalls sitting in the corner with his hands on a pulley chain attached to the ceiling. The prisoner was lowered a few centimetres, just enough to stand on the soles of his bare feet. He raised his head, his dank hair plastered over his forehead. He looked up imploringly at Luke, saying nothing.

‘This,’ said Colonel Petrov, indicating the prisoner as if he were just some sort of inanimate object, ‘is our gift to you. This man is a member of Cherny Nozh. You understand what that means?’

‘No.’

‘Cherny Nozh, Mr Carlton, means “Black Knife”. It is an extremist organization here in Russia. We caught him only a few days ago. He is in contact with “extreme people” in your country, in UK, people who are planning something big. How do we know this?’ For the first time Luke saw Colonel Petrov smile. To him, it looked more like a wolf baring its teeth.

‘We know this,’ Petrov continued, ‘because we have been monitoring his communications. And so …’ He stopped speaking as he strolled over to a wooden table and chair placed in the corner of the lockup, beckoning Luke to follow him. Petrov moved casually, like a man who had all the time in the world. There was a laptop on the table and he opened it now, plugging in what looked like a USB device. He entered a series of rapid keystrokes, then issued a command to those behind him, not even bothering to turn round. Luke heard, ‘Razvyazhitye yevo,’ which meant nothing to him, but now there was a flurry of activity around the prisoner. For a moment he thought they were going to start on him again and this time he braced himself to intervene. But instead he saw two guards untie the man’s wrists then put their arms around him to half carry him to the chair, sitting him down in front of the laptop. His head sagged and he kept murmuring something in Russian, but he stopped as Petrov spoke to him at length.