The present painting depicts a procession of ships on the River Thames on 4 June 1771, King George III’s thirty-third birthday. A group of boats of several colours, sizes, and ranks, navigate under and past Westminster Bridge bearing flags and standards to celebrate the King’s anniversary. It was during George III’s reign that the ceremony of Trooping the Colour was first used to mark the official birthday of the monarch, a tradition that continues today.

At lower right, Prince Frederick’s Barge is visible, bearing the Royal Standard, presumably transporting George III and Queen Charlotte. The barge was originally designed by William Kent for George III’s brother, Frederick Prince of Wales, and after his death in 1751 was used by successive monarchs until 1849. This painting also shows Westminster Bridge around twenty years after its inauguration in 1750. Samuel Scott painted the bridge several times during and immediately after its construction, before it was redesigned by architect and civil engineer Thomas Page (1803-1877) following structural issues, and reopened in 1862.

Several versions of this composition by followers of Samuel Scott exist, including at the Walker Art Gallery, Liverpool, and the Worshipful Company of Drapers, London. A painting depicting the procession further down the river by the Tower of London is in the Yale Center for British Art, New Haven. The subject and composition can be compared to Canaletto’s Westminster Bridge, with the Lord Mayor's Procession on the Thames (1747; New Haven, Yale Center for British Art), which presumably influenced Scott and his followers. Depictions of parades and pageants on the Thames became common and sought-after in the 18^th century, attractive due to their integration of naval subjects, cityscapes, and colourful and fancy historical and ceremonial scenes.