Roy Precious - Antiques & Fine Art has dated this piece to the 17th Century.
As the sitter was considered a great beauty in her time, several portraits of her exist.

This particular pose was much in vogue and was associated with a fashionable melancholy and deep, sensitive thoughts.
LETITIA ISABELLA SMITH, COUNTESS OF RADNOR (c.1630-1714)
She was the daughter of Sir John Smith, or Smythe, of Bedborough, Kent and his wife, Isabel Rich, youngest daughter of Robert Rich, 1st Earl of Warwick and Sidney's 'Stella'. They had four sons and five daughters, including the Hon. Francis Robartes (?1650-1718), the composer and scientist, whose portrait by Kneller is at Lanhydrock and Laetitia Isabella Robartes, who married firstly, in 1669, the 2nd Earl of Drogheda, and secondly, around 1679, the playwright William Wycherley. After the death of the Earl of Radnor at his celebrated house (previously Danvers House) in Chelsea, the sitter was married, as his second wife, to her Chelsea neighbour Charles Cheyne, 1st Viscount Newhaven (1625-98).

Lady Robartes, as she then was, was described by Pepys as "a great beauty indeed", and she is also the subject of a celebrated story in the Memoirs of Count Grammont. According to the latter, she momentarily excited the desires of James, Duke of York, when: "in the zenith of her glory. Her beauty was striking". But her husband resisted all the bribes to connive with his being made a cuckold, until he was finally forced to take her off on a pilgrimage to St. Winifred's Well, which was said to cure women of barrenness, and: "did not rest until the highest mountains in Wales were between his wife and the person who had designed to perform this miracle in London".

SIR PETER LELY (1618 - 1680) was the most important portraitist in the reign of Charles ll, although he had painted portraits throughout the Commonwealth, Principal Painter to the King, he painted everyone of importance, maintaining a busy and active Studio to help with the huge demand for his portraits. Members of his Circle, and his Followers, many of them talented artists in their own right, emulated his style to supply this constant market.
SIZE: 38 x 33 x 2.25 inches framed.
PROVENANCE: London Private Collection
Roy Precious - Antiques & Fine Art has dated this piece to the 17th Century.
Roy and nadine precious: specialists in portraiture from the 16th to the 20th century. Established in 1972.
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