For someone born without the ability to empathise, sometimes Peter can be surprisingly intuitive. Reflexively I touch my left hand. The scar has long since healed, though from time to time I still feel phantom pains in fingers I left on a cellar floor nine years ago, nature’s sly little joke at my expense. Years of physical therapy have given me back more of my dexterity and skill than I’d dared hope, but I’ll never be a world-class surgeon again. I’m a jobbing butcher now: heart bypasses, shunts, valve replacements. I still save lives, but no one comes to me for their Hail Mary pass: the inoperable surgery no one else would have the ego or ability to perform. I’m nothing special now.

And yet, oddly, I’m OK with it. I wasn’t at first, of course. It took me years to come to terms with my loss. But I’ve learned there’s something deeply satisfying about grooming the next generation of raw talent. I feel the pride of a parent when one of my students beats me at my own game.

‘It’s four years today,’ Peter says suddenly.

As if I could forget.

‘Yes,’ I say.

‘Do you still miss him?’

Grief isn’t something that abates. You simply learn to live with it, in the spaces around it. A scar forms: to the outside world, it looks as if you’ve healed. But the pain never goes away.

And yet, somehow, you adapt. You manage with eight fingers instead of ten. You survive. Grief shapes you in unexpected ways: you are never the person you once were, but you figure out a way to move through the world.

Tom loved me unconditionally. He saw me for who I was, and it’s only now he’s gone that I’m able to understand what that really meant and see myself through his eyes. I am flawed, so very flawed, but I’m not the sociopath I once believed myself to be. I didn’t think myself capable of great love, but the overwhelming, all-encompassing nature of my grief after Tom died showed me that loving him was my greatest achievement. He always knew that however damaged I was, no matter how many mistakes I made, I was also fundamentally a good person. Even the very worst thing I ever did, killing my father, I did to save a life. I gave up the thing that mattered most to me besides my family – my career – for my son. I tried. Can any of us ever do more than that?

‘I’m sorry,’ Peter says. ‘I’m sorry that he’s gone.’

Intellectually, I think he means it. It’s not his fault he’s unable to feel it.

‘Did you see my talk?’ he asks.

‘Your SET talk?’ I say. ‘Yes. I watched it online.’

He leans forward, his hands clasped loosely between his knees, eyes alight. ‘Did you like it?’