I thought of Charlotte and her parents, working all the hours they could to protect their standing in their community. I imagined my friend poring over her schoolwork for hour upon countless hour, determined not just to protect what she had, but to climb further up the ladder, to become one of the ruling class by dint of willpower, education and a self-discipline I couldn’t begin to comprehend. It wasn’t just ambition that motivated her, I suddenly realised, but also fear. Fear of slipping from their nice house to just another ordinary one in the community and from there to one close to the walls and the warning sirens and from there to outside the gate and therefore beyond protection, becoming …

Xena snapped her fingers in front of my eyes.

‘Earth to Ashleigh,’ she said. ‘Are you receiving me?’

‘Sorry,’ I said. ‘I was thinking about a friend. You were saying? The people in the communities are guarded. They’re guarded from …’

‘From us,’ said Xena. ‘The final tier. The outcasts. We’re the ones who don’t fit into the top two levels. The ones who can’t get a job in security. Or choose not to. The ones who’re free to live however we want. So we forage, we barter, we trade for everything, look after our own little … you’d probably call it a tribe. We say family.’

She pointed to a large house with a massive gate and a high fence surrounding it. It was about a hundred metres ahead on the right of the road.

‘Headquarters,’ she said. ‘Where the leaders care for our people. This district is ours. Other districts belong to other families. We defend our territory, they defend theirs. And then, of course, there’re the people who don’t belong anywhere. The wanderers. Now they’re really a worry. Especially if you bump into one on a dark night.’

‘This is what you talked to my brother about? That day in the park.’

‘Among other things. He wasn’t as … ignorant as you, but he sure had a lot to learn.’

I nodded. I was beginning to realise that despite my expensive education, maybe because of my expensive education, I knew virtually nothing at all. As if to prove the point, the closer we got to Xena’s Headquarters, the more baffled I became.

‘What is that noise and what is that disgusting smell?’ I asked.

Xena appeared genuinely puzzled.

‘That squealing,’ I added. It was like metal scraping along metal, the kind of high-pitched noise that sets your teeth on edge and feels like pain against the temples.

She laughed. ‘Oh, that noise. That smell. Pigs. Dozens of ’em. We keep ’em round the back. Their crap’s no good for the vegetables, but we compost it down. Couple of months it’s okay to use.’

‘You put up with that noise and smell for compost?’

‘Nah. We put up with it for bacon.’