‘The best!’ He wriggles free and looks up at me.

Assume it’s fine. Always, always assume it is fine. And Charlie really has had a good day at school; Ms Simmons comes out to the playground especially to tell me. ‘He did really well in our maths test,’ she says. ‘He said he’d been practising with you.’

My son is looking up at me, his face open, eager, hopeful. Kids need praise like flowers need the sun, I know that. Genuine praise, loving praise.

‘That’s great. I’m so pleased,’ I say, smiling at both of them, my son and his teacher. ‘It’s lovely to hear when Charlie is doing well.’

I stoop down and take his hand in mine.

My perfect, flawless, healthy son.

To prove it to myself, I take Charlie out to eat for dinner. We walk right across Brockwell Park and down to Herne Hill, where there’s a fish and chip restaurant that Charlie has loved ever since we came here for the first time a couple of years ago.

We go out to eat like this so rarely, trying to get by on my single wage. And because being out in public like this puts me so on edge. But I’m remembering something else the psychologist told me last year. You have to test your fears. Really test them, push them far enough to really prove them wrong.

When we get to Ollie’s fish restaurant, I let Charlie order whatever he fancies. He wants the children’s portion of cod and chips, and I choose the same, only adult-sized. I know I need the calories. Once we’ve ordered our drinks, Charlie busies himself colouring in the paper placemat. I try not to let it remind me of the tests they gave him, paper and pencil exercises, tests of function and intellect.

Lately I’ve been letting my mind run away with me. These worries about Charlie. I need to get a hold. Mike Bernard’s call has restarted everything – everything I thought I could let go. How did I think I could just walk away? After the way I let Sarah down before? And now am I going to let Marianne and Alastair down too? And anyone else out there who knew her, who cared? I told myself I wouldn’t leave it up to the coroner. How can they answer the questions we all need answered? But if I’m going to keep investigating Sarah’s death, then I need to be sure that my mind is clear, strong. Sitting across from him, I steady my breathing. I sit there, hands in my lap, concentrating – in-breath, out-breath – until my heart beats a slow, steady rhythm. I time it for a minute, then one minute more. I know how to do this. I knew that I could.