The painting is by Dutch master Peter Lely, official artist to Charles II, from the 1660’s.  Those same art historians think the King concealed it behind a secret sliding panel in the royal bedchamber at the Palace of Whitehall, not least because Villiers was already married, but also because she was as promiscuous as he was.  It was the heyday of the courtesan and the libertine. (By 1698, the Palace of Whitehall was enormous, but it was destroyed by fire that year.)

Villiers lived to be 69.  Not so her male equivalent, John Wilmot, the Earl of Rochester, to whom she was related.  By the age of 33 he was dying (in 1680), possibly from syphilis and alcoholism.  But his erotic poetry is startling even today, which is why it’s been available really only since the 1960’s.  A couple of his more catchy poems include “Signior Dildo” and “Mistress Knight’s Advice to the Duchess of Cleveland in Distress of a Prick.”  Here is a sample from “The Imperfect Enjoyment” – imperfect because, as the last two lines show, lovers have to take a break from it sometimes.

But whilst her busy hand would guide that part
Which should convey my soul up to her heart,
In liquid raptures I dissolve all o’er,
Melt into sperm and, and spend at every pore.
A touch from any part of her had done’t:
Her hand, her foot, her very look’s a cunt.

Now languid lies in this unhappy hour,
Shrunk up and sapless like a withered flower.

The portrait above of Rochester is the only well known image we have of him. It is by the Flemish painter Jacob Huysmans who, like Lely, resided in London. It prompted novelist Graham Greene to call his biography of the poet Lord Rochester's Monkey, which Greene wrote in the early 1930's but couldn't publish till the 1970's.