“They want the Jenny in one piece,” Hester told him. “They won’t risk using rockets.”

“Want the Jenny? Why would anyone want this old wreck?” The tension was making Pennyroyal tetchy. When Hester explained he shouted, “This was Anna Fang’s ship? Great Clio! Almighty Poskitt! But the Green Storm worship Anna Fang! Their movement was founded amid the ashes of the Northern Air Fleet, sworn to avenge the people killed by London’s agents at Batmunkh Gompa! Of course they’d want her ship back! Merciful gods, why didn’t you tell me this ship was stolen? I demand a full refund!”

Hester shoved him aside and went to the chart table. “Tom?” she said, studying their maps of the Tannhausers. “There’s a gap in the volcano-chain west of here: the Drachen Pass. Maybe there’ll be a city there we can put down on.”

They flew on, climbing into thin air above the snowy peaks and once skirting dangerously close to a plume of smoke that belched thickly from the throat of a young volcano. No pass, no city did they see, and after another hour, during which the three Fox Spirits steadily narrowed their lead, a flight of rockets came flashing past the windows and exploded just off the starboard bow.

“Oh, Quirke!” cried Tom — but Quirke had been London’s god, and if he couldn’t be bothered to save his own city, why would he come to the aid of a battered little airship, lost in the sulphurous updrafts of the Tannhausers?

Pennyroyal tried to hide under the chart table. “They are firing rockets!”

“Oh, thanks, we wondered what those big explodey things were,” said Hester, angry that her prediction had proved wrong.

“But you said they wouldn’t!”

“They’re aiming for the engine pods,” said Tom. “If they disable them we’ll be dead in the sky and they’ll grapple alongside and send a boarding party across…”

“Well, can’t you do something?” demanded Pennyroyal. “Can’t you fight back?”