Copley, the foremost artist in colonial America, was virtually self-taught as a portraitist. Having established a successful practice in Boston, he was encouraged to visit Europe in 1774. After a year's travel he settled in London and began to specialise in religious and historical subjects, becoming a member of the Royal Academy in 1779. A fellow American artist, Benjamin West, who had become Historical Painter to the King in 1772, helped Copley to obtain the commission from George III to paint the three youngest royal princesses. Copley's sense of the significance of the opportunity is reflected in the sheer scale of the painting, for which he made many studies. As the royal children and pets grew tired of the numerous sittings they had to endure, West had to reassure the King that Copley 'must be allowed to proceed in his own way'.

On the left is 9-year-old Princess Mary (1776-1857) striking a tambourine to amuse her 2-year-old sister, Princess Amelia (1783-1810), who is seated in the carriage (adorned with her monogram PA), beyond which is the 8-year-old Princess Sophia (1777-1848). They are playing beneath a vine-covered arbour with parrots picking at grapes above them; in the distance the Round Tower of Windsor Castle is visible in the evening landscape.

The painting is full of carefully observed detail of surfaces and textures and captures the affectionate relationship between the sisters and their natural high spirits. However, it was judged harshly by contemporary critics, most of whom found its ebullience unsuited to royalty and considered the composition unfashionably cluttered. To the modern eye, Copley has managed to capture the energetic spirit of childhood in a painting that is undeniably rococo in spirit. 

Signed and dated J. S. Copley 1785