The ancient and sinister Tower of London that lures more than 2 million visitors a year would be an inspiration for any writer, especially one with the kind of whimsical imagination from which sprouts a world of ravenous ravens and a 181-year old tortoise called Mrs. Cross whose tail has been replaced by a parsnip.

Not to mention a Beefeater who collects exotic rain, patronizes a tower tavern called The Rack and Ruin and the ghost of Sir Walter Raleigh, who pollutes the place by his nightly smoking.

Ms. Stuart has concocted a marvelous confection of a book in which she writes of a unique cast of characters. The occupants of the royal menagerie, established in the tower in the 13th century, range from a royal polar bear that fished for salmon in the Thames to a golden snub-nosed monkey with titian hair christened the duchess of York.

What could have been heavy-handed whimsy has in this writer’s hands become a charming spoof that portrays the life and rather tragic times of Balthazar Jones, overseer of the tower’s royal menagerie and a man whose living quarters, while historic, provide evidence of just how uncomfortably damp life could be in the good old days.

Jones, weighed down by grief over the death of his young son and his failing marriage to Hebe Jones, is a member of that exclusive group known as Beefeaters who are the official guardians of the tower. In the 16th and 17th centuries these yeoman warders, as they were known, not only guarded royal prisoners but sometimes had the task of torturing them.

Jones’ duties are less onerous, but he is less than enthusiastic to hear that his responsibilities have been expanded to include managing a new royal menagerie of the animals given to the monarch as gifts to be moved on the queen’s orders from the London zoo to the tower. The queen, it is explained,considers it rude to return gifts, however unlikely.

A palace equerry sips tea and nibbles scones supposedly handmade by her majesty while describing to Jones the kind of animals he will be caring for. While emphasizing the seven centuries of tradition of a royal menagerie at the tower, the man from the palace notes that her majesty is “rather partial to tortoises” and is aware that Jones is already in possession of the venerable Mrs. Cross. Left unmentioned is the fact that the voracious ravens of the tower, which favor blood-soaked bread in their diet, had chewed off Mrs. Cross’ tail.

Jones’ late son had come up with the ingenious idea of implanting a parsnip where it showed and nobody seemed to notice, perhaps with the exception of Mrs. Cross. According to the emissary, due to be included in the new menagerie are toucans from the president of Peru, a zorilla which is a “highly revered yet uniquely odorous skunklike animal from Africa,” marmosets from Brazil, flying possums that “get depressed if you don’t give them enough attention,” a Russian “glutton” that looks like a small bear and has a huge appetite and a Komodo dragon that “is carnivorous, can take down a horse, and has a ferocious bite.”

In addition, the equerry announces, there will be some crested water dragons known as “Jesus Christ lizards” sent from the president of Costa Rica, and an Etruscan shrew from the president of Portugal that is “the smallest land mammal in the world, can sit in a teaspoon and is so highly strung it can die from being handled.”

On a final note, the man from the palace cautions Jones to keep the lovebirds separated. “They hate each other,” he explains. Jones finds none of this cheering news, especially when the removal of animals from the zoo to the tower turns into the kind of chaos that involves the mysterious disappearance of an entire flock of Argentinian penguins which the beleaguered Beefeater has to justify to the public by explaining they are at the vet’s office.

It is a tribute to Ms. Stuart’s skill that she interweaves a little poignancy into her hilarious story, with a touching account of the death of Milo, small son of Jones and his wife that has resulted in their estrangement.

However, even the character of Hebe Jones is threaded with dark humor because she works at the Department of Lost Property at the London underground, where the lost are neatly packaged yet often never found or even sought. The author digs into that gold mine. The department’s most frequent customer is “cloud thin” Samuel Crapper, who comes to retrieve a lost tomato plant and doesn’t realize that four of its tomatoes had already been eaten on toasted cheese.

And there is the account of how the ashes of his dead wife were restored to a man crushed by their loss. He is not only overjoyed but promptly goes out and plants the urn in his back garden. There is even what passes for a happy ending because the queen decides to send the menagerie back to the zoo, with the exception of the Etruscan shrew that died without anyone noticing.

Jones is reunited with his wife, and finds he misses the bearded pig that used to snuggle up to him between games of roll the grapefruit. But he is consoled that the depressed wandering albatross cheers up when it finds its mate is still waiting for it at the zoo.