Athénais: the Real Queen of France by Lisa Hilton

The splendour of the National Gallery's current Madame de Pompadour exhibition contrasts with the neglect of another celebrated king's mistress. Indeed, the name of the Marquise de Montespan is virtually erased from the annals of Versailles, as I found when trying to locate the apartments where she and her lover, Louis XIV, had laughed at courtiers passing by. She wasn't mentioned, explained the guide, because she had "tombée de grace".

Considering that she was an inspiration to the Sun King in the creation of Versailles, her eclipse is all the more bizarre. Lisa Hilton, in her racy yet erudite biography, lays the blame on her successor, the religious bigot Mme de Maintenon, whose back-stabbing of her former friend reads like a present-day smear campaign.

Beautiful, witty and flamboyant, Athénais de Montespan was maitresse en titre to Louis XIV for 12 years. One of the aristocratic Rochechouart de Mortemart family, she caught his eye as he was beginning to tire of Louise de La Vallière. But Athénais had a difficult husband who created appalling scenes. His existence was a reminder that Louis was committing double adultery, a more serious sin than simply being unfaithful to his wife. Maintenon, whom Athénais had rescued from poverty to be governess to the royal bastards, cultivated his guilt.

Athénais was passionately in love with the king, not just with the riches of her position – though she enjoyed spending. The most expensive gift was the Chateau de Clagny, built at a cost of £7m in today's money, but she was more often in her Versailles apartment adjoining the king's. Louis's libido required instant satisfaction.

Athénais was never afraid of the king, but she was afraid of losing his love. The stress of uncertainty led to overeating, drinking and displays of temper. What did for her was the affair of the poisons, in which a number of the nobility were accused of murdering their relatives. Hilton argues persuasively that Athénais was only marginally involved. One supplier of poisons provided her with "love powders", and may have arranged a blasphemous mass when she was seeking to displace the previous mistress. Egged on by the minister, Louvois, the witches began to accuse Athénais of lurid practices: black masses, poisoned gloves, sacrificed babies. The king gave no credence to the wilder rumours and, in pensioning her off, gave her the title of Superintendent of the Queen's Household, with the privilege of being permitted to sit down in the presence of the man by whom she had had seven children.

After the death of the queen, Maintenon was secretly married to Louis. She was a political meddler, and encouraged him to persecute the Huguenots. But everything comes with a price: Maintenon abhorred sex but was now married to a man who required it frequently and, schooled in her religious scruples, no longer sought it outside the marital bed. Her plea to her confessor for an excuse to avoid "those painful moments" was refused.

Maintenon was obliged to receive the royal member twice a day until the age of 70. Her rival's discomfort must have appealed to Athénais's sharp wit.