When he was fourteen, Rory won a prize – a real one. It was the equivalent of a child’s Nobel prize for science. I remember seeing him walk on to the stage of a university lecture hall, a small huddled figure in that vast space. He smiled coyly as he shook the Dean’s hand and I looked on, slowly warming through with jealousy until I was glowing white. It was a prize I was too old for. People clapped. A man spoke about the ‘completely innovative’ approach to one of the world’s most complex theoretical physics questions. The maths in it was difficult but the truth was that he was so bright that he could slice straight into the physics while the others were still stuck on the numbers. But that wasn’t the only reason he’d won. It had been my solution, from one of Dad’s monthly debates. And though I’d harvested it from some other physicists I’d been researching in answer to the debate, Rory didn’t know that. As far as he knew he’d just stolen my answer.

I was made to go along to the presentation. Afterwards, Dad had promised us, him, a steak at a new South American steakhouse. Later, once the steak had been eaten and he’d been slapped on the shoulder by Dad – later, once we were back at home watching Dad drink whisky and Mum wine – later, once the trophy had been nudged into centre spot on the mantel, Rory, to whom I’d said nothing all evening, walked up to the fireplace and picked up the trophy and placed it at my feet.

‘This is yours,’ he said, avoiding my eye. ‘Dad,’ he said then, still looking at the floor. ‘This is his. It was his answer.’

Dad nodded and took a sip of whisky. ‘It belongs to you both. Not for the science – but because you improve each other.’

I tried to rationalise what he’d done. He was younger. He was allowed to make mistakes like this. I might have done the same in his position. In fact I never reminded myself that I’d cheated him. Or that he’d have won anyway. Instead I sat with the trophy at my feet, ashamed of it and me and him all at once. Hours later, Dad was sleeping in his chair, snoring, his glass balanced on his chest. Mum, watching Dad closely, put down her glass and came to me. She took my face in her hands and then turned to do the same to Rory. Her hair was greying, I noticed, and she had started wearing her glasses permanently then.

‘I won’t leave you,’ she said. ‘Not ever.’

I opened my mouth to say something but the words wouldn’t form.

‘You don’t have to say anything,’ she said, smiling sadly.