‘So there’s more gravity, because of all the weight.’

Maria glances at us for a second and then thanks us. Her look says: ‘I’m stuck here, 20,000 kilometres from home, living with mad people.’

We show her the rugby league on the television and make her Vegemite toast, which she describes as ‘most interesting’. I show her a wattle tree and point out the bright yellow flowers. ‘Fascinating, isn’t it,’ I say, ‘that this, too, is a eucalypt?’

‘Actually,’ says Jocasta, ‘it’s an acacia.’

‘Well, that’s right,’ I say. ‘An acacia, thought to date from the time of dinosaurs. Older than anything you’d find in Europe.’

I decide I should give her a break from the learning—just as soon as I’ve taught her a little geology. Having once read the back of a Tim Flannery book, I feel pretty well equipped and so, as we help her into the house, I explain that Australia is the oldest land on the planet, possibly older than the planet itself, I can’t be quite sure, but certainly older than Germany.

‘Everything’s been worn down over time. Imagine something just wearing you down, hour after hour, day after day.’

‘Yes,’ replies Maria, limping up the stairs, ‘I can see how that might work.’

Will Batboy’s host parents be like this: forcing him to express joy in every detail of German flora, fauna and geology? The days go past. He rings home after about a week. I say to him: ‘I bet we overdid it when we imagined them living this really rural existence. You know, the trombone choir and the pig slaughtering. Now you’ve met them, I bet it’s not like that at all.’

‘In fact,’ he says over the phone, ‘it’s more extreme than I imagined; more remote, more traditional.’ He explains how his family never buys soft drink: the main drink is apple juice, crushed from their own orchard. They grow all their own food, right down to their own wheat, barley and spelt, an ancient grain which the mother grinds into flour. Only last night they had pizza with the base made from hand-ground spelt. For entertainment they really do have the church trombone choir, of which all the family are members. The only thing we didn’t understand is that a trombone choir, for some reason, has more than just trombones. It has a variety of brass instruments. The whole village, he says, is heavy with brass instruments.

And yet, says Batboy, he’s having fun. And he really admires his host father, Volker, and the rest of the family.

Ten weeks later he arrives back home. We greet him at the airport, thrilled to have him back. He has vastly improved German. In fact, his problem now is his English. ‘My father, Volker, sent me out to collect some, some, you know, Sägemehl,’ he says to us, the English word entirely lost to him. He acts out a sawing motion. ‘You know, the white stuff that comes out of the tree.’

‘Sawdust,’ suggests Jocasta.

‘That’s it,’ says Batboy, before running ahead with his sentence only to get tangled up once more, this time in a chainsaw. ‘My father, Volker, cut the tree down with a, you know, a Kettensäge.’

But it’s this ‘my father’ stuff that gets me. I know the exchange student is supposed to embrace the new family, but does Batboy have to be quite so enthusiastic? As the days go on, it’s all Volker this and Volker that. Maria was never like this about me, despite all the effort I put into her education.

We stand at the back door, looking out at our small suburban backyard. ‘On our farm,’ says Batboy, ‘we have an orchard. And our own small plantation of pines to supply the family with timber.