"It's like this," he starts, and bites into a buttered roll, delaying his further explanation for the space of chewing and swallowing.

"The whole world froze over when I was little. Only people still alive are the ones who got onto this train that goes round the world and never stops. Up in the Front, that's where the rich bastards are, the ones who paid first class. In the middle, there's the people who got economy class tickets, they work for the Front. And in the Tail, there was us. The ones who got on by lottery."