Princess Mary, depicted here at the age of 19, was the fourth daughter of George III and Queen Charlotte. She was also painted in miniature by the artist Andrew Robertson, who recorded in his diary the difficulties he encountered: 'beautiful creature, most difficult to paint, fidgets about, now sits steady one moment – affable and laughs'. In this portrait the artist, Richard Cosway, finished the head only, lightly sketching the background. The soft texture of the hair contrasts with her bright, sparkling eyes. A finished version, by another miniaturist, Anne Mee (née Foldsone), is in the Royal Collection (RCIN 421057).

Like her sisters, Princess Mary led a sheltered early life at Windsor Castle, and also spent time nursing her younger sister Amelia at Weymouth. The King was very attached to his daughters and reluctant to let them marry and leave home. In 1816, a marriage was finally arranged for Mary to her cousin William Frederick, Duke of Gloucester (1776-1834). When she died in 1857, Queen Victoria wrote: 'Her age, and her being a link with bygone times and generations … rendered her more and more dear and precious to us all, and we all looked upon her as a sort of grandmother.'

Richard Cosway (1742-1821) was born in Devon, the son of the headmaster of Blundell's school, Tiverton. The family were prosperous, and owned a woollen business and property. At the age of 12, Richard was sent to London to study drawing under Thomas Hudson at Shipley's drawing school. He entered the Royal Academy Schools in 1769 and exhibited at the Royal Academy between 1770 and 1806. He married Maria Hadfield in 1781, an accomplished artist herself. The couple had one daughter, who died at the age of seven. Richard Cosway's portrait of Maria Fitzherbert attracted the attention of the Prince of Wales who appointed him as his official miniature painter in 1786 and general advisor for the decoration of Carlton House, his residence in London. In 1811, however, Cosway lost the Prince's favour and his eyesight began to fail. He was an eccentric and outlandish in his behaviour and dress, but was an astute collector and acquired a fine collection of old master drawings. His miniatures are painted with a delicacy and fine modelling, and he developed the technique of using transparent pigments which allows the natural luminosity of the ivory to shine through.

Catalogue entry adapted from Masterpieces in Little: Portrait Miniatures from the Collection of Her Majesty The Queen (1992) and George III and Queen Charlotte: Patronage, Collecting and Court Taste (2004).