The wife if the Grand Sénéchal was automatically a lady in waiting to the Queen. Diane was present at the births of the Royal Children, and was especially close to the third youngest, Henri.

Henri, whose childhood was marred by years of captivity in Spain, developed a strong affection for Diane which, from his 15th year on, became more and more ardent. His marriage to Catherine de Médicis in 1533 did nothing to efface the chivalrous attachment of this timid youth.

When Anne de Pisseleu began to threaten Diane, Henri came to her defence. The beautiful widow became Henri's mistress.

When, in 1536, his brother died and young Henri became the heir to the throne, Diane's situation was enhanced as much as was the Dauphin's. Henri elected also to appear only in black and white (as you can see in the portrait on this page) under the pretext of platonic affection, making the crescent - which was attributed to the divine huntress his emblem and adopting the famous monogram with H and D interlaced.

Note the entwined crescents on this fireplace:

The Grande Sénéchale and Henri's wife, Catherine, were coldly polite to one another. After all, Diane was the official governess of the children finally born to Catherine after eleven years of infertility. Catherine accepted all, resigned herself and bit her lip as she awaited her revenge. This revenge almost came during Henri's lifetime. From letters published after the death of all parties involved, Catherine hatched a plot with the Duke of Nemours whereby he, in a moment of gaiety, would throw a glass of water in Diane's face. A dupe would be accused of having replaced the contents of the glass with quicklime, which would permanently disfigure Diane and render her a prisoner to a world of veils and gauzy curtains for the rest of her life. The plot was discovered, at least in part. The Duke was driven from court, though eventually allowed to return; after all, he had merely been a dupe himself for the jealous queen.

Diane was officially acknowledged as his mistress three years after the marriage. The age factor added insult to injury. As Henri's wife, it was of course her duty to produce an heir (or better yet, several of them), preferably male, as a daughter could not inherit the throne in France. Catherine appeared to be incapable of fulfilling her duty in this respect. Diane realized there was no love lost between her and Catherine, of course, but she was also aware that if Henri's marriage were annulled because there was no heir, he might have to marry someone even less accommodating. She made an arrangement with Catherine, agreeing that on some evenings Henri would spend several hours in Diane's bed, then go to Catherine's for a while, then return to Diane's bedchamber. We are told that Diane also gave Catherine some “practical hints". This evidently did the trick, because the future François II was born in 1544, followed by the future Charles IX in 1550, and the future Henri III in 155l, plus several other children.

Diane de France is a mystery who has divided the opinions of historians. One accepted story is that she is the daughter of Diane and Henri. Another story says that fling with a girl named Filippa Duci resulted in the birth of a daughter. Filippa was sent to a convent, and the child, named Diane, was raised with the rest of the royal children by Diane de Poitiers. In researching my book, I have come to know and understand Diane's personality, and I an of the opinion that Diane de France was indeed the daughter of Diane and Henri.

Upon the death of François 1 on the 31st of March, 1547, Henri became King of France. Suddenly, Diane was the most powerful woman in France! She was the first and only royal mistress in French history to have a coin minted in her likeness:

Pictured here is an exterior view of the Louvre in Paris (which was a royal palace before a museum), with the HD clearly present:

Diane possessed an extreme intellect and a political astuteness to the point that the King trusted her to write many of his official letters and to even sign them jointly with the one name: HenriDiane. She was in fact, the "brains behind the throne".