‘Come on, Hitch,’ I said. ‘Newgate! The human zoo. Chamber of horrors. Monument to the cruelty of this great city. “Abominable sink of beastliness and corruption.” Come on! You’re one of this city’s leading historians! You’re telling me you didn’t know that Newgate was still down there, buried alive under the Old Bailey? I don’t believe you, Professor.’

‘You knew?’ Whitestone said to him, her voice hard and cold. ‘Is this true?’

He ran his hands down his coffee-stained shirt.

‘No,’ he said. Then he hesitated. ‘Not immediately . . .’

Whitestone exploded. ‘Jesus Christ!’

‘It seemed so unbelievable at first,’ he said. ‘That they could possibly be so bold. But – as a place of execution – Tyburn was followed by Newgate, and so it made perfect sense.’

‘When did you know?’ Whitestone said, white-faced with controlled fury.

‘From the start,’ I said. ‘He knew from the start.’

‘No!’ he said. ‘Not from the start!’

‘You obstructed this investigation,’ Whitestone told him. Her voice was not much more than a whisper but I had never seen her so angry. ‘You nearly got one of my team killed. Do you know what that means, Professor? You’ve obstructed a murder investigation. You’ve perverted the course of justice. You’ve concealed evidence. Do you think you could do three years’ hard time, Professor Hitchens? I’m not sure you would make it.’

There was true terror in his eyes now. Not the fear that I might give him a slap across the cakehole. The fear that he could end up in jail.

‘I didn’t know from the start, I swear it,’ he insisted. ‘It was only from the time they took Abu Din. When he got away and they showed pictures of the Sangin Six on those walls . . . the walls of . . .’

‘Newgate,’ I said for him. I shook my head. ‘What’s in it for you? Why keep it a secret? Who are you to let these creeps deal out death and judgement?’

I saw the anger flare in his eyes.

‘And who are you to deny it? Look at the filth they hanged, Max. Mahmud Irani – a child groomer who disfigured his own daughter! Hector Welles – a rich banker who killed a child in his sports car! Darren Donovan – a junkie who ended the life of a war veteran!’

I grabbed him by the scruff of his neck.

He flinched away from me.

‘I’ve done nothing wrong,’ he whimpered. ‘I never lied to you! I never wanted anything bad to happen to you, Max!’

I was struggling to control my rage. I had him by the lapels and I would not let him go. He held up his hands to protect his face. I could see his fingers, stained dark yellow with nicotine. But I was not going to hit him. And he knew it.

The knowledge emboldened him.