Roy Precious - Antiques & Fine Art has dated this piece to the 18th Century.

The brushwork is typical of the artist's late style..assured and sophisticated..with quick, loose, almost flickering, brushstrokes.
LADY MARY WORTLEY MONTAGU, née Pierrepont, (baptized May 26, 1689, London, Eng.—died Aug. 21, 1762, London), was the most colourful Englishwoman of her time and a brilliant and versatile writer.

Her literary genius, like her personality, had many facets. She is principally remembered as a prolific letter writer; she was also a distinguished minor poet, always competent, sometimes glittering and genuinely eloquent. She is further remembered as an essayist, feminist, and traveller.

She suffered an attack of smallpox while she was still a young woman, and she later pioneered in England the practice of inoculation against the disease, having noticed the effectiveness of this precaution during a stay in Turkey.

Lady Mary had the British Embassy’s surgeon inoculate her young son. Back home in 1721, while a global smallpox epidemic was killing people from Britain to Boston, Massachusetts, she had him inoculate her daughter (born in Turkey), and publicised the benefits of inoculation against bitter hostility, including physical violence.
Opponents of the procedure derided it as Oriental, irreligious, and a fad of ignorant women, so Lady Mary's fame for it was both mixed and short-lived.
SIR GODFREY KNELLER (1646-1723) was the most distinguished painter of baroque portraits in England.
Born in Lubeck, he trained with Bol and Rembrandt, coming to London in 1676.
By 1679 he had painted the King and remained the most famous and successful portrait painter in England until his death.
In 1688 he was made Principal Painter to the King and was knighted in 1692 and a made a baronet in 1715.
His style had a profound influence on British portraiture.
SIZE: 39 x 31 inc. frame.
PROVENANCE: * Christie's, London, 26 July 1985, lot 105.
London Private Collection.
Roy Precious - Antiques & Fine Art has dated this piece to the 18th Century.
Roy and nadine precious: specialists in portraiture from the 16th to the 20th century. Established in 1972.
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