‘He’s going to get on,’ she said. ‘Really get on.’ She kissed my cheek and laughed.

‘It’s early days,’ I said, thinking that we shouldn’t feel too proud. But I couldn’t stop the smile that was spreading across my face.

Kathryn gave the book a shake. ‘Gold stars. We should reward him.’

‘We’ve only just bought him a bike.’

She gave my upper arm a playful pinch. ‘Don’t be such an old stick-in-the-mud. He deserves a little something. As encouragement.’

After a moment I thought of a suggestion. ‘How about taking him to the power station?’

She frowned.

‘As a reward,’ I continued. ‘I think he’d like it.’

‘Would he?’

‘Power. Cables and engines and trains – it’s what boys like, isn’t it?’

‘I suppose.’

‘I can show him what I do.’

‘Do you think he’ll enjoy it?’

‘We’ll go tomorrow.’

It’s always breezier on the site. The wind cuts past the towers like a blade in the winter. But that Saturday it seemed to be warmer than it had been for weeks, and I let Robert unzip his anorak. His cheeks glowed. His thick hair, which his mother had allowed to grow too long, hardly moved in the wind.

I guided him around the bottom of the first cooling tower. Water roared as it poured down the concrete sides. We stopped for a moment while I explained how it worked. Every time he looked up at me, I thought he must be listening, but he didn’t ask any questions until we were back on the road towards the turbine hall. Then he said, ‘Why is there dust everywhere?’

I didn’t notice that any more, the piles of soot that gathered along the kerbsides and made the puddles black. I didn’t notice the way it caught in the back of your throat. I’d forgotten that when I first came to the power station I’d wondered why the snot was black when I blew my nose.

‘It’s from the coal.’ I pointed to the black hill of coal dust. ‘That,’ I said, ‘is what heats the water.’

He looked at it and frowned, but when I asked him if he’d like to go closer, he shook his head and reached for my hand.

‘Are we going to see the fire?’ he asked.

‘Fire?’

‘The fire the coal makes.’

I laughed. ‘We’re going to see where I work. I don’t work with the fire.’

His fingers were moist as they tugged at my hand. ‘I want to see the fire.’

Of course. He wanted to see the engine of the place. He was a young boy. He wasn’t interested in buttons and levers. He wanted pumps and pipes and generators. He wanted noise and power, the hot centre of the place.

I decided I would impress him: I’d take him into the turbine hall.

‘We’ll go and see the fire,’ I said, leading him into a side entrance and up the stairs to the viewing gallery door, ‘but it’ll be noisy. OK?’