"The start of season two really is all about Montespan," Louis XIV actor George Blagden told RadioTimes.com

We have already met the king's mistress in season one of Versailles, Madame de Montespan (Anna Brewster), but in season two this ambitious noblewoman is tightening her control. Two years have passed and now Montespan is the most powerful woman in France. 

"We start to see how that influence that she's gained and that favour that she's gained with the King really starts to affect him and his mind," Blagden explained. "All of the day to day decisions that he has to make are filtered through the Montespan filter, and we even see him taking her advice on some rather monumental decisions and ignoring his most trusted valet, Bontemps."

Did Madame de Montespan really exist?

Yes. Her full name was Françoise Athénaïs de Rochechouart de Mortemart, Marquise of Montespan, and she was the king's lover in the 1670s.

Being the "maîtresse-en-titre" meant that she was the monarch's official mistress and was entitled to apartments at Versailles. The relationship was no secret, an arrangement which would have seemed pretty normal for a king of France (Louis' father had at least two official mistresses in his time). 

Who was the real Montespan?

Montespan (1640-1707) first met the king in the early 1660s, but she was not a major player in Louis' love life until 1666 or 1667. In the intervening years, she had married the Marquis de Montespan and given birth to two children, and carried out her duties as a lady-in-waiting to the Duchess of Orléans at the Louvre. She was already known as a beauty, an excellent dancer, and an amusing conversationalist. 

She was also ambitious. It seems Montespan set her sights on becoming the king's mistress, slowly but steadily ousting Madmoiselle de la Valliere from the top spot until 1674 when her position was made official. 

In the meantime, Montespan had already given birth to several of the king's children. These illegitimate kids had initially been sent off to live with Montespan's friend Madam Scarron (who later became the king's official mistress in her own right). But when Montespan's position was made official, Louis legitimated his children, and ultimately recognised six of their seven sons and daughters (one had already died in childhood).

Having consolidated her position at Versailles, Montespan became the most powerful woman in France. Her social circle "became the epicentre of the court, its pleasures and its fortunes, a source of both hope and terror for ministers and generals,” as memorist Saint-Simon wrote. She had the ear of the king, and she had the position to shape France's cultural life by patronising artists such as Moliere. 

What was her downfall?

Holding the king's interest was always a challenge (just take a look at any of her predecessors in the job) and Montespan apparently alienated the king with her unpredictable temper. There were also other women at Versailles snapping at her heels, and she had put on weight from her nine pregnancies. She was out of favour, losing access to the king's private chambers and losing the spotlight at court. 

At this time, she also got caught up in the "affair of the poisons", a dark period at Versailles from 1677 to 1682 when assassinations were rife and many prominent aristocrats were charged with poisonings and witchcraft.

Unfortunately for Montespan, she was accused by the doomed midwife La Voisin in 1679 of buying aphrodisiacs and performing black masses. There was no evidence, but this was a period of paranoia and the incident badly damaged her reputation.

She finally retired from the court in 1691, moved to the convent of Saint-Joseph in Paris, and died in 1707 at the age of 67.

Versailles begins on Friday 21st April on BBC2 at 9.30pm