The Serpent and the Moon:

Two Rivals for the Love

of a Renaissance King

By Her Royal Highness

Princess Michael of Kent

Touchstone, 405 pages, $42.50

Overcrowded royal marriages hold a particularly enduring fascination no matter in what century they take place, as British royal Princess Michael of Kent ably demonstrates in her latest work, The Serpent and the Moon. Set in France during the first half of the 16th century, the book charts the lives and relationships among King Henri II of France; his wife, Catherine de Medici; and Henri's lover, Diane de Poitiers.

From the outset, the author declares her enormous admiration and a sense of personal connection with Diane, "the Moon." Her antipathy for "the Serpent" -- Catherine de Medici -- is also strong. Personal favouritism notwithstanding, the author's confidence and passion for her subject have inspired a hugely entertaining book.

While the story of the three protagonists and the vicissitudes they faced is the stuff of High Renaissance drama, the author is careful to give the compelling narrative a lucid and well-described mis en scène.

Diane was born in 1499; her mother and Catherine de Medici's were cousins. The young noblewoman was placed in the household of Queen Claude, consort to François I, the great Renaissance king. At 15, she married the brilliant, 55-year-old widower, Louis de Brézé, one of the richest, most important and ugliest men in the kingdom. It was an excellent if perhaps physically unappetizing match for the blond, blue-eyed teenager, who was already drawing attention to herself not only for her beauty, but for an elegant self-possession that far exceeded her years.

Henri and Catherine, his future wife, were born within a few weeks of each other in 1519. Catherine was orphaned only days after her birth and Henri lost his mother when he was 4. Both children then suffered periods of imprisonment, being held hostage in separate conflicts. Catherine was incarcerated in Florence while Henri endured four years of hardship in various Spanish fortresses. When at last he was released, Henri had changed from a cheerful boy into a sullen and withdrawn teenager. Diane, now widowed, made it her mission, at the King's request, to draw his least favourite son out. Her kindness, patience and humour soon made their mark on this awkward boy, and it is no wonder the prince became ensorcelled by her.

A pawn in strategic plans for the Italian peninsula between Pope Clement VII and François I brought the arrival of the non-royal Catherine de Medici as a bride for Henri. This did not change the prince's feeling for "his lady" Diane. He simply ignored the dumpy little bride, who, having suffered much the same miserable childhood as her husband, loved him desperately from the moment she met him. This was her tragedy; believing she had found a family and home, the clever but physically unattractive young woman soon found herself supplanted by a sophisticated beauty.

When Henri acceded to the throne in 1547, he made Diane richer than even she could ever have hoped; though time had taken its toll on her famed beauty, her hold on the king's heart remained as firm as ever. While there is no evidence that she ever really tried to influence him when it came to politics, Diane enjoyed enormous powers of patronage and greatly enriched herself and her kin.

The author highlights Diane's virtues, her fidelity to Henri, her staunch support of Catholicism, her sublime taste, her modern adherence to matters of hygiene and a unique ability to appear cool and remote, as though on another plane. Indeed, she promoted endless allegorical references to herself as Diana, the chaste goddess of the hunt, for that was precisely how she wished to be seen.

The near-deification of Diane by Princess Michael is sometimes hard to swallow, particularly as there is a corresponding demonizing of Catherine. For example, the author divines that when Catherine was silent she must have been hatching evil schemes. It is also worth noting that Diane's hatred of Protestants might have had something to do with the fact that the "heretics" called her a whore. In truth, Diane was an extremely smart cookie with good looks, extraordinary taste, a head for figures and a generous lover.

Little credit is given to the humiliated queen and her dignified acceptance of the mistress's supremacy. The king insensitively had their entwined initials, "H & D," carved and painted wherever he could, and Catherine knew that to complain would gain her nothing. If she accepted "our friend" -- as the king called Diane -- she would at least be pleasing her husband.

Finally the triangle, so long established, became an entirely unremarkable feature of court life. Each woman conceived a healthy respect for the other; Diane took care of the Queen when she was ill or pregnant, and Catherine always behaved with great politesse to her rival. Both also knew that it would be better not to destabilize a formula that might expose the king to unknown predators. The idea that Diane protected Catherine out of goodness to the Queen is nonsense; it was to ward off a beautiful young royal replacement who might not tolerate the liaison with Henri.

This is book is a cornucopia of fascinating, well-researched period detail, much of it about the exquisite paintings, sculptures and buildings commissioned by Diane, notably her glorious Renaissance palace at Anet. Added to the fortune in cash, jewels and other treasures Henri gave his mistress was the extraordinary Chateau of Chenonceau, a place also much desired by Catherine, and the snub provoked a rare but bitter cry from the Queen.

After Henri's sudden and tragic death in 1559 in a jousting accident, Catherine, far from being vengeful, simply traded her own less attractive but more valuable estate of Chaumont with Diane for Chenonceau, and banished her from court. The mistress knew that her days of power were over. Diane might have been queen of Henri's heart, but Catherine was Queen of France.

Leonie Frieda is the author of the recent biography Catherine de Medici. She lives in London.