Double portrait of a boy and girl, full-length, the boy in a brown suit and breeches, holding a whip, and the girl in a red dress with a sash of flowers, seated on a rocking horse waving a flag, a landscape beyond

Widely travelled in Europe during the first quarter of the 18th century, Mercier settled in England circa 1716, becoming Principal Painter to Frederick Prince of Wales in 1729. In 1736, however, Mercier was dismissed and escaped London's competitive portraiture market for a more receptive audience in the country. The artist's patrons during this period included the Duke of Leeds, who acquired four pictures; Sir Robert Hildyard of Winestead, who bought a portrait and two 'fancy pictures', and Thomas Worsley, who acquired five portraits (Ingamells and Raines, op. cit., p. 4).
The decade from 1740-50, while he was based in York, was the greatest period of activity for Mercier - over 160 pictures survive from this time. It was during these years that he seemed to turn purposefully towards the 'fancy picture' genre he first started to favour in the late 1730s. The term 'fancy picture' was coined in 1737 by the art critic and historian George Vertue with specific reference to Mercier's work and the influence of French rococo pastoral pictures, such as those of Greuze and Boucher. Employed loosely throughout the 18th century, the phrase 'fancy picture' was used to describe charmingly contrived genre scenes of sentimental realism, incorporating the artist's own whimsy and imagination or references to contemporary literature, with figures shown in various roles and guises.