Now I am back in the interview room and this time I listen to their names: Rachel Blake, not Rochelle. And Simon Conway, detective inspectors, both of them. The interview starts again from the top. The initial statements are all the same, as if I am caught in a system glitch: introductions, caution, the right to a solicitor, all explained meticulously once again. I avoid their eyes through it all, concentrating my gaze on my fingers.

‘Just before the break,’ says Rachel Blake, ‘you were telling us about witnessing an attack. On a woman.’

‘Yes,’ I say. I am still puzzled about why they’d decided that I was mentally unwell. Nothing that the custody sergeant asked me gave me any hint.

‘Well, I’m going to be asking you about that later. For now, I want to talk to you about the attack on a gentleman by the name of Kenneth Squire. Does that name sound familiar to you?’ she asks.

‘No,’ I say. This is plainly a mistake. ‘Who is he?’

‘He is a person, like you, shall we say, of no fixed abode. If I may show you a photograph? The suspect is now being shown exhibit RB/1, a photograph of the victim. Do you recognise this man?’

I stare at the picture and my blood freezes. It is unmistakeable – it’s the man from the park, the drunk. A shot of his face, with his eyes closed. There’s a long surgical scar running along his throat. But it is him.

‘Er, yes. I. Well. No, I don’t know him as such but I do recognise him,’ I say slowly.

‘From where?’ Blake asks, her voice flat.

‘I’m not sure,’ I say. ‘Just from around.’

She continues. ‘Mr Squire was found earlier this morning in Hyde Park. He was stabbed in the neck and would have died if he hadn’t been spotted by a runner. Do you have any idea how he might have received that injury?’

‘No,’ I say.

‘That cut on your eye, Mr Shute. How did you get it?’

I put my fingers to it. The stitches lie proud of the surface but I resist the urge to scratch them.

‘I fell,’ I say. They know more than they are saying, but at this moment I cannot fathom what they know or how they know it.

‘Fell where?’ Blake says, her voice even and steady.

‘I don’t know,’ I say. ‘People like me fall. We fall and we get up and we fall again. East Dulwich? Camberwell, maybe. Who can say?’

‘You, Xander, you can say. In fact, you did say – to the police who took you to the hospital – that you fell in Hyde Park.’

My memory of the detail of that conversation is patchy. I could have said that to the officer, I probably did, but I can’t remember.

‘That’s it then,’ I say, hiding my fists beneath the desk.