“Well, Percy,” said his sister, drawing his attention to her presence. “What do you think?”

“Why name the craft after a comestible and then decorate it like a Coccinellidae?”

Rue knew better than to attempt reasoning with Professor Percival Tunstell. “Because I like it that way.”

Percy wrinkled his nose at her and then, distracted, leapt forward. “Do be careful – those documents are hundreds of years old!”

Rue summoned Percy’s valet with a subtle gesture. “Virgil, be a dear and steer him up that gangplank and down below into the library, would you, please? Spoo here will show you the way.”

Spoo obliging appeared at Rue’s elbow and nodded at the young valet. “Oi up, me duck?” she said, or something equally unintelligible.

Virgil looked askance at the soot-covered girl, near his own age but remarkably scruffy and laddish by comparison. “Good afternoon,” he said, remembering his manners. Then he looked up at Rue, panicked. “Himself won’t like it if this one goes anywhere near those there scrolls.”

Rue grinned. “Ah, good. Spoo, follow those trunks, pretend to be helpful and try to touch them but don’t actually do so.”

“If you say so, captain.” Spoo, irrepressibly good-natured, trotted off to do exactly as she had been instructed.

Percy instantly panicked and ran after the girl as she rendered – what Percy was certain was – smudgy doom upon his trunks and satchels of books. Everything else was forgotten as he followed the sootie’s stubby form in gangly worry. Virgil brought up the rear carrying a wicker picnic basket that was yowling in protest, and a good quality hatbox. At least Percy would have one top hat on board. And his cat.

“Good. That’s him safely ensconced,” said Rue.

“You’re not worried he’ll escape?” Prim watched her brother with affectionate exasperation.

“I’ve given instructions for the footmen and porters to wall him in with his own books. By the time he reads his way out, we should be ready for float off.”

“You’ll leave a feeding hole?”

“I’m not a monster.” Rue looked up in time to see yet another conveyance barrelling towards their not-so-secret location. “Speaking of monsters.”

This contraption was no horse-drawn carriage but a steam-powered locomotive of a most unusual design. It was insect-like in appearance, constructed rather like a pill bug, although it was not intentionally decorated as such – like The Spotted Custard – but only appearing bug-like out of necessity. It was more utilitarian than beautiful, its exterior comprised of darkened metal panels shelling into one another like scales. It belched steam from below this carapace, and smoke from two stiff antennae.

The steam roly-poly subsided to a stop and a hatch at its top popped open. Quesnel Lefoux’s boyish head poked out.

“Good afternoon, ladies.” He tipped his hat. He, of course, was impeccably well turned out.

“Mr Lefoux, how do you do?” Prim gave the inventor a warm smile.