“’Course you do,” said Jones gently. The sadness and homesickness that filled the two girls was sudden, but it didn’t feel like it came out of nowhere. It had been there many hours, underneath everything, and now that things were calmer, with the beautiful view below them, it sort of ambushed them.

“My mum must have the police and everything,” Deeba said.

“Actually, I wouldn’t worry too much about that,” said Jones.

“What do you mean?” said Zanna.

“Difficult to explain. The Propheseers’ll tell you.” The girls shook their heads in exasperation. “Just…I wouldn’t worry yet.”

Deeba and Zanna were quiet. Sensing their mood, Curdle snuffled up to Deeba’s foot. She picked up the little carton and, ignoring its sour smell, stroked it.

“Yet?” Zanna said. Conductor Jones looked evasive, and started muttering something about air currents and tacking and the directions. “You said,” Zanna insisted, “don’t worry yet ?”

“Well,” he said grudgingly. “Londoners can get out of the habit of thinking about some things. Things that come here. But I wouldn’t worry yet.”