[1] Active in England for most of his working life, Mercier is considered one of the first practitioners of the Rococo style, and is credited with influencing a new generation of 18th-century English artists.

He was appointed principal painter and librarian to the Prince and Princess of Wales at their independent establishment in Leicester Fields, and while he was in favour he painted various portraits of royalty, and no doubt many of the nobility and gentry.

Prince George is represented with a firelock on his shoulder, teaching a dog his drill, while his little brother and sister are equally occupied in a scene that is aptly used to point a patriotic moral embodied in some verses subjoined to the plate, of which the concluding couplet is as follows: Illustrious Isle where either sex displays Such early omens of their future praise!In 1733, Mercier painted a Portrait of 'Frederick, Prince of Wales, playing a violoncello, and his Sisters'.

In the painting 'The Sense of Hearing', 1744, women are playing violin, violoncello, harpsichord, and flute in the Yale Center for British Art.

[8] In 1739 he relocated to York, where he focused on 'fancy' pictures concerned with domestic virtue[9] and also practised portrait painting for over ten years, before returning to London in July 1751.