“Hag-kissers! Slack-jaws! Dirt-gobblers! Mumblebums! Dolts! Filthy blackguards! Bulging scumbags! Gusset-sniffers! Gibbering loonies! Puppy-munchers!”

Trailing behind Miss Mayson, the men reached the other side of the room. The young woman unlocked a door, threw it open, and ushered them through. The portal slammed shut behind them and she leaned against it, opening the umbrella. “That's quite enough of that, I think! My apologies, gentlemen.”

They stood in a very spacious rain-swept yard beside a row of cages, each containing an upright wheel. In each wheel there was a dog-all greyhounds-sprinting at top speed. There must have been at least twenty of them, and the rumble of the spinning wheels drowned out even the noise of the rain.

The greyhounds were known as runners, and they formed the other half of the British Postal Service. Where the parakeets communicated spoken messages, the dogs delivered letters, racing from door to door with the missives held gently between their teeth. In fact, they were unable to stop running, and even when they arrived at a delivery destination they jogged on the spot until the letter they carried was taken. They were also voracious eaters, and any person using the service was obliged to feed them.

“They've just gone to sleep,” Miss Mayson said, gesturing toward the animals.

“They run in their sleep?” Swinburne asked wonderingly.

“Yes, which is why I had the wheels put inside their cages. It's better than having them racing around the yard. The swans are over there.”

She indicated the far end of the enclosure, where nine breathtakingly huge birds stood in high-roofed pens. Their heads were poised, about fifteen feet up, at the top of elegantly curved necks. Their beady eyes watched the group as it approached them.

“Don't worry. They're almost tame.”

“Almost?” Trounce asked, doubtfully. “Somehow, I don't find that very comforting.”

“If they were any wilder, they'd bite your head off before you could blink. They're aggressive by nature.”

Trounce smoothed his mustache with his fingers.

“But four are tame enough to fly, yes?” Burton asked.

“Five,” Spencer added.

“Yes, sir, though you might struggle a bit. They're a touch headstrong.”

“Let's get them buckled up. We have to work fast.”

Miss Mayson crossed to a shed from which she produced harnesses and big folded box kites. Then she picked up a long, thin wooden cane, returned to the pens, and used it to drive out five of the enormous white birds.

“Down!” she commanded, while slapping one of the swans on its side with the rod. It obligingly squatted, and, while Spencer held the umbrella over her, she showed the men how to attach the long reins to the base of the bird's neck, passing them over its back. Swinburne, who'd flown swans before, assisted her by buckling the ends of lengthy leather straps to its legs and clipping the other ends to one of the box kites which Burton and Trounce had unfolded.

While they worked, the king's agent instructed his companions: “Look out for litter-crabs.”

“Why litter-crabs?” Trounce asked in a puzzled tone.

“I noticed that the end of Saint Martin's hadn't been cleaned,” Burton responded. “Now I know why. The litter-crabs were tempted away from it by the mega-dray. You know how the contraptions tend to follow behind the horses, cleaning up the manure. I dare say they're still on its trail!”

“Good thinking, Captain!” the policeman exclaimed.

Miss Mayson helped Constable Bhatti into a kite. He sat on the canvas seat, slipped his boots through the stirrups, and took the reins. The woman showed him how to control the bird.

A few minutes later, all five men were in position.

Miss Mayson stepped back. “Half a mo!” she cried. “Wait there-I have an idea!”

She ran back along the yard and into the training centre.

“What's she up to?” Burton grumbled truculently, but even as he spoke she reappeared and hurried over to them.

She held a small blue and yellow parakeet in her hand.

“All messenger parakeets are identified by a postcode,” she said. “This is POX JR5. She's one of the new breed. As long as she knows you, she'll be able to find you. She doesn't even need your address. You can use her to communicate between the kites. She'll keep up with the swans-she's the swiftest of all my birds. Tell her your names!” She held the parakeet out to each of the men in turn.

“Captain Richard Burton.”

“Odorous thug!” the bird whistled.

“Detective Inspector William Trounce.”

“Ponderous buffoon!” it cheeped.

“Algernon Charles Swinburne.”

“Illiterate bum-pincher!” it cackled.

“Constable Shyamji Bhatti.”

“Nurdle-thwacker!” it squawked.

“Herbert Spencer.”

“Angel-faced beauty,” it crooned.

“My goodness!” Miss Mayson exclaimed. “Was that a compliment?”

Burton blew out a breath. “Please,” he said, “there's no time for this!”

She gave a small nod and placed the parakeet on Burton's shoulder. It hunkered down and he felt its little claws sinking into the soggy cloth of his overcoat.

“Good luck!” the young woman said, stepping back. “Constable, call in tomorrow and tell me all about it!”

Bhatti smiled and nodded. “Get yourself inside and dry off,” he advised. “Your slippers are wet through!”

Sir Richard Francis Burton snapped his reins the way she'd shown him. His swan stretched out its wings, ran five steps forward, and, with a mighty flapping, soared into the air. The leather straps of the harness uncoiled, snaked up after it, jerked taut, and his kite shot upward.

Thrown violently back into his canvas seat, the king's agent found himself rising at phenomenal speed into the sodden atmosphere. The rain pelted against his face. His swan spiralled higher and, when he glanced back, he saw that his colleagues were following behind.

The chase was on!

T he water-laden air jabbed cold needles into Burton's face, but despite being hatless-for, like the others, he'd placed his headgear into a spacious pocket at the back of the kite-he actually felt unpleasantly warm; a sign that his malarial fever was developing rapidly. He tried to stay focused but a peculiar sense of disassociation was creeping over him.

“Bloody git-face,” POX JR5 mumbled.

The five giant swans began to circle over the western end of Orange Street. Visibility was poor in the rain so the men flew them close to the rooftops, except for Swinburne, who, despite being the most experienced flier, was having problems controlling his unruly bird. He was currently somewhere overhead, inside the low blanket of cloud.

Tracking the mega-dray proved easier than Burton had anticipated.

It was Bhatti who spotted the trail. He steered his swan in beside Burton's, but the kites, at the end of their long tethers, were flying extremely erratically due to the wind and beating rain, making it impossible to shout across to one another.

Burton spoke to the parakeet: “Pox! Message for Constable Shyamji Bhatti. Message begins. What is it? Message ends. Go.”

The brightly coloured bird launched itself from his shoulder. A few moments later, when the constable's kite tumbled upward past his own, Burton saw that the messenger was already squawking into the young policeman's ear.

The explorer shifted his hips, trying to stabilise his vehicle. It was foul weather for flying!

The parakeet returned. “Message from dribbling sponge-head Constable Shyamji Bhatti!” it whistled. “Message begins. Look off to the right, snot-picker-the bloody litter-crabs are all along Haymarket. Message ends.”

Burton told Pox to take the message to Trounce, Swinburne, and Spencer. He then sent his swan wheeling to the right and along Haymarket. He passed over four of the large eight-legged, steam-driven street cleaners and spotted a fifth at the end of Piccadilly. Yanking at the reins, he veered to the left and followed the thoroughfare. He soared past a sixth crab, a seventh, an eighth, and Green Park hove into view. The ninth litter-crab was clearing up a mountain of steaming manure outside the exclusive Parthenon Hotel; after that, all the way to Hyde Park Corner, he didn't see a single one.