Roy Precious - Antiques & Fine Art has dated this piece to the Before 1700 period.
However, the pose and oval were used by several artists, most notably Sir Peter Lely.

When the painting went for conservation a hardboard backing was removed and, painted on the lining, in what appears to be an 18th century hand, is an inscription naming the sitter as Miss Trenchard, painted by William Wissing in 1682.

Below are excepts from research by Adam Busiakiewicz, art historian:-
" I believe that your portrait very likely to be Philip(a) Trenchard , wife of Sir John Trenchard (1649-1695).
I believe Sir John's wife, Philip(a) daughter of George Speke esq. of Whitelackington, is the best candidate.

She was born in 1663/4 and married Sir John in 1682 - the year that this portrait was made. I think that this portrait was probably made to celebrate their marriage,
I think that there is little doubt that this is a picture by Wissing, dating to 1682.

The quality of the picture is rather good, with lots of character in the face. The blushing cheeks are well painted too. It has far more depth that a Beale. I have attached a few comparisons.
Wissing did paint decorative ovals, although far less often than Beale.

The drapery is good too and lacks the solidity you find in Beale.
The strong political connections between Sir John Trenchard and William III, who was eventually painted by Wissing many times, makes this connection rather interesting.
Of course, we have lots of portraits of William and Mary that Wissing produced from his studio with great speed. One often finds that Wissing eventually settled down into a rather stiff and formulaic manner (as many court painters often did), but, this particular portrait is filled with character and freshness."
SIR JOHN TRENCHARD (30 March 1649 – 27 April 16950 was one of Stuart England’s most accomplished and controversial aristocratic statesmen or “principal secretary of state for life”.
He belonged to an old Dorset family. He was born on 30 March 1649 at Lytchett Matravers, near Poole, to Thomas Trenchard of Wolverton (1615–1671), and his wife Hannah née Henley (d. 1691). His grandfather was Sir Thomas Trenchard of Wolverton (1582–1657), who was knighted by James I in 1613. John Trenchard entered Parliament as member for Taunton in 1679. He associated himself with those who proposed to exclude the Duke of York from the throne, and attended some of the meetings held by these malcontents. It is possible he was concerned in the Rye House Plot. In fact, he was arrested at one of the events in July 1683, but no definite evidence was brought against him so he was released.
When Monmouth landed in the west of England in June 1685, Trenchard fled from England to Groningen, Netherlands. Around 1687-1688, he was pardoned , and able to return home. Again he entered Parliament, but he took no active part in the Revolution of 1688, although he managed to secure the good will of William III. On 29 October 1689, he was knighted by the King, and made Chief Justice of Chester. In 1692, he was appointed Secretary of State.
On 10 November 1682, he had married: Philippa Speke (1664–1743), daughter of George Speke of White Lackington, Somerset.
Sir John died on 27 April 1695 at Kensington, London, and is buried at Bloxworth, Dorset.
Phillipa remarried and lived for another 50 years.
WILLIAM WISSING (1656 - 1687) After Lely's death in 1680, Wissing emerged as his most important pupil. Wissing’s royal sitters include Charles II of England, Queen Catharine of Braganza, Prince George of Denmark and the Duke of Monmouth.
SIZE; 39 x 34 inches inc.frame.
PROVENANCE: descent in a Dorset family. (It is plausible that this of portrait might have descended down with the Trenchard family, of Lychett Maltravers, Dorset)
Roy Precious - Antiques & Fine Art has dated this piece to the Before 1700 period.
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