'The most improbable things are completely useless," he says, matter-of-factly.

"Or at least the ones we should look for are. It's more fun to search for something you want, rather than something you need, isn't it?"

But he thinks.

"If we're going outside, we could search for a spring, or a cave, or some sort of unlikely creature, although there seem to be rather a lot of those already here."