So the next instant there we were. The sudden change took my breath away. Green space all around us. A pleasant breeze blowing. There were a few dog-walkers dotted about, and on the far side some little kids and their parents in the playground, and about a hundred metres away some boys were having a kick-about. They were going to get the shock of their lives in a minute, I thought.

‘How big do you want to go?’ I said.

‘I dunno – about twenty metres high?’

‘Sounds about right to start with. ’Course, we can always go bigger if we want to.’

‘’Course we can.’

My heart was pumping away like a crazer and my stomach was doing cartwheels. I couldn’t quite believe what we were about to do.

‘Ready?’

‘Ready.’

‘We’d better stand a bit further apart,’ I said. ‘Otherwise when we start to grow we’ll bump into each other.’

‘Oh, yeah.’ He moved off, about fifteen metres away.

‘Ready?’

‘Wait – I just thought of something. You better wish our clothes grow too, or we’ll burst out of them and be naked. And that’ll be embarrassing.’

‘OK. I wish me and Evan were giants, twenty metres high, and our clothes still fitted us, and we were all in the same proportions as now.’ I didn’t want to be like a great long skinny piece of string, I wanted to be an actual giant, like in fairy tales.

And so . . . we started to grow.

It was the weirdest feeling. I could see the ground getting further and further away, as if I was going up in a lift or a cable car, but at the same time I could feel the ground sort of expanding under the soles of my growing feet. And I could see Evan swelling up beside me, an idiotic grin of excitement on his face. We were inflating like a couple of giant balloons.

Only – this was the weirdest thing of all – we weren’t getting lighter, like a balloon would as it filled up with air. We were getting heavier. I could feel my head drooping on my neck, like my neck was too feeble to hold it up properly. And my body was getting so massive my legs couldn’t support it properly. Even though my legs were growing too, they weren’t up to the job of keeping me upright, I was just too heavy. They started to buckle, I could feel them giving at the knees. I tried to wave my arms to help me keep my balance, but they were almost too heavy to move, it was like trying to wave tree trunks around.

I was going to fall, and I knew that falling from this height, at this weight, would be serious. I mean, really serious.

I mean, like, fatal.

I saw my own expression of panic mirrored on Evan’s face as he tottered helplessly around.