Rare glimpse of the Stubbs portrait of a (rather racy) lady

She rose from humble and shadowy origins in London's seedy nether world of brothels and booze to become one of the trusted circle of the Prince of Wales.

She rose from humble and shadowy origins in London's seedy nether world of brothels and booze to become one of the trusted circle of the Prince of Wales.

The Prince was so besotted with Lady Laetitia Lade that he commissioned a portrait of her from George Stubbs, one of the greatest artists of the day, to hang at his London home two centuries ago.

Now the rarely seen painting of this extraordinary woman, which is normally hidden away in the private rooms of Windsor Castle, is to go on public display at a major exhibition of Stubbs's work at the National Gallery.

Like many women of the era, only fragments of her life remain - the rest is lost in the mists of time because chroniclers tended to dwell on the menfolk of the age. But her foul mouth gave her some notoriety at the time and gave rise to the phrase "to swear like Lady Lade". She was also renowned as a gifted horsewoman. Stubbs's painting shows her calmly dealing with a rearing horse while seated side-saddle, a tricky feat.

It is not even clear when she was born, but Lady Lade, who was born Laetitia Derby, is understood to have worked as a servant in a brothel in her early years. Through her underworld connections she became the mistress of the dandy highwayman John Rann.

After he was tried and hanged for his crimes, she became the mistress of the Duke of York and then moved on to his friend Sir John Lade, a society figure who as a child was the subject of a poem by family friend Dr Johnson.

It was through Sir John that she became close to the profligate Prince of Wales - George Augustus, later to become George IV - who employed him as his racing manager.

"The Prince of Wales seems to have been quite obsessed with her," said author Robin Blake, whose book George Stubbs and the Wide Creation is published on Thursday. "But he probably respected his friend's marriage. He flirted with her and sent her presents from Bath."

The Prince commissioned Stubbs to do 14 paintings. "The 14 subjects were essentially a review of all his interests in life, so it is telling that she is one of them, but whether he took it any further we will never know."

The National Gallery's exhibition opens on 29 June.