Oil on canvas, in a fine Regency frame, 218.44cm by 144.8cm.
The sitter was the daughter of Peter Burrell of Langley Park, Beckenham and former wife of the 8th Duke of Hamilton.
In 1800 she married, as his third wife, Henry, 10th Earl of Exeter who, the following year, was elevated to the marquessate, as 1st Marquess of Exeter.
The artist, who was self-taught, supported his family at a young age with his pastel portraits.
In later years, as a portrait painter in oils, he enjoyed the patronage of the Prince Regent and ultimately, a reputation as the most fashionable portrait painter in Europe.