‘And nothing. I didn’t hear back from Six. Lang went about his business as normal. A couple of weeks before the meeting, I decided to lift the sneaky prick myself. Give him a taste of this.’ He waved the cattle prod in the air, like a magic wand. ‘Find out what he was planning.’

‘You were going to torture David Lang?’

‘That was the plan. Then my handler got in touch with me out of the blue. Demanded an emergency meeting. Not like him at all. He said he had big news. When I got to the meeting, the guy was very twitchy. He looked panicked.’

‘What did he say?’ asked Casey.

‘He told me to leave Lang alone. I asked him why. My handler said Six was going to deal with him. I told him I had ways of making Lang talk, but he claimed Six had a better plan. When I asked him for details, he just smiled and said that his brother was going to have a nasty accident. His exact words.’

‘That’s why they used Novichok to kill Freddie Lang,’ Casey interjected. ‘To make it look like Moscow was behind the attack?’

‘Exactly.’ Gregory pointed a finger at her. ‘You’re a sharp one. ’

‘Why would Six want to poison him?’ said Bowman. ‘Why not just arrest David, if they knew he was up to something dodgy?’

‘Isn’t it obvious? They needed a way of turning the screw on Lang. Pressure him into calling off the deal with the Russians. Subjecting him to a hard interrogation wouldn’t get them anywhere. So they decided to kill his brother and pin it on the Russians. Make it look like Moscow was planning a double-cross.’

Bowman shook his head in disbelief. ‘But . . . that means Six carried out a chemical weapons attack. On their own soil. People were poisoned, for fuck’s sake. Hospitalised.’

Gregory shrugged. ‘Best way of getting David Lang to spill his guts.’

‘Who else knew about this?’ Webb demanded.

‘Only a handful of people. The higher-ups at MI6, myself. The guys tasked with the wet work. And your boss, of course.’

‘John knew?’ Bowman said. The bayonet sank deeper into his guts.

‘He runs the Cell. He’s plugged into everything that goes on inside Vauxhall,’ Gregory replied. ‘He knows all their dark secrets. John would have known about it from the start.’

‘He wouldn’t lie to us.’

‘Are you sure about that?’ Gregory parted his lips into a cruel smile. ‘I hear David Lang took a nasty fall from his apartment yesterday. That was John’s doing, I imagine. In fact, I wouldn’t be surprised if he’d planned to kill Lang all along.’

‘No.’