Roy Precious - Antiques & Fine Art has dated this piece to the 17th Century.
The inscription has been examined under UV light and, although strengthened, looks original.

The WITHYPOLLs were a family of very rich merchant adventurers with interests in Bristol and Genoa. Based in Ipswich, owning Christchurch Mansion, now the art gallery.
Sir Edmund Withypoll married Frances, daughter of Sir William Cornwallis of Broke.

Eldest son Sir William (about whom much online); younger son Henry or Harry, baptised Brome 26 Aug 1602.
Between 1646 and 1652 Henry married Mary, daughter of Sir Robert Carey.
His wife's family were much involved in the Netherlands on behalf of the States General.

A letter survives dated 10 Jan 1638, Breda, endorsing Capt. Withypoll.
And in 1646 he was described as "residing mostly in Holland where he has a company of soldiers under him". In 1648 he was elevated to the rank of Major in the English regiments in the service of the Dutch States General.

He had died by 1670.
GERRIT VAN HONTHORST (1592 – 1656) was a Dutch Golden Age painter; born in Utrecht,
He built a considerable reputation both in the Dutch Republic and abroad. Queen Elizabeth of Bohemia, mother of Prince Rupert, sister of Charles I of England, then in exile in the Netherlands, commissioned Honthorst as a painter. Through her he became known to King Charles, who invited him to England in 1628.

After his return to Utrecht, Honthorst retained the patronage of the English monarch, painting for him, in 1631, a large picture of the king and queen of Bohemia and all their children. His popularity in the Netherlands was such that he opened a second studio in the Hague, where he painted portraits of members of the court. These were large studios, where the work of his assistants included making replicas of Honthorst's royal portraits.
SIZE: 37.50inch framed height 3.25inch framed width (95.25 cm framed height 8.25 cm framed width)
PROVENANCE: Collection of Lord Berners, Faringdon House, Oxfordshire. (See last 3 images).
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.
You can view the stock and full dealer information on the Roy Precious - Antiques & Fine Art Profile Page