‘Me too.’ He moves closer so he can hold a wire still for me. ‘That’s why I like science.’

‘Did you used to take stuff apart when you were little?’

‘All the time! My toys, my bike … Mum’s coffee machine.’

‘Once I noticed the DVD player was sticking so I took the back off it.’ I look back up at him. ‘I was five.’

‘Maybe you’ll be an engineer when you’re older.’

I shrug. ‘I don’t think so …’ He passes me a screw and I say, ‘What do you think you’ll do?’

‘I’ve not thought that far ahead … Maybe I’ll mend toys.’

I press the cow and it quacks. ‘You’ll have to get better at it.’

He tuts and peers at the circuit board. ‘I’m sure you were doing the cow.’

Once we’ve got all the cows mooing and the ducks quacking we put the toys back together. Ed tells me about how he once stuck a bath toy to his forehead to make his brother laugh, but when he pulled it off he was left with a suction mark. ‘It was in Year Eight,’ he says. ‘I had to walk around school with this big red circle on my forehead! Don’t you remember?’

I shake my head. I don’t bother telling him that I was probably too intimidated by Ed and his friends to even look at him in Year Eight.

‘Well, I can remember something that happened to you in Year Seven,’ he says.

‘What?’ I feel a flutter of panic inside as I try to remember if I did anything particularly humiliating back then. When I started secondary school, I was so clueless I actually wore a ‘This girl loves science’ T-shirt on non-school-uniform day – it had two big pink thumbs pointing up at my face – and I read out my ‘Day in the Life of an Atom’ poem in assembly. But then the eye-rolling began, and the sniggering … And then Mr Harper said ‘photosynthesis’ in that voice …

‘You and your friend won a prize for making a go-kart,’ says Ed.

‘Oh, that.’ My panic slips away. That go-kart was awesome. We were the only girls in the Formula One club and our kart was so fast we were picked to go to the regional finals. ‘Yeah, we did win a trophy, but then we got beaten in the finals by a boy from another school.’

‘I really wanted a go on that go-kart,’ Ed says, then he tests the toy hammer by banging it on the floor. He nods to the corner of the room. ‘Does Elsa usually sleep in a dog basket?’

I look over and see that Elsa’s crashed out in Pongo’s bed. ‘Only sometimes.’ I go and tuck a blanket round her. Pongo hardly uses his bed so it isn’t too hairy.

Ed’s rummaging through my toolbox. ‘We need some tape.’

‘It’s in my room.’ I push Pongo’s nose away from Elsa. Now someone else is in his bed he wants to get in there too. ‘No, Pongo,’ I say, and he flops down next to her. I’m just giving his wiry tummy a scratch when I hear a door open … My bedroom door!