Ann Trotter posed for this portrait in 1788, the year after her marriage to Robert Trotter, who was subsequently Postmaster-General for Scotland. She sat for the artist in Spring 1788, but it was delivered a year later. 18th-century portraitists would typically only focus on painting the main features of a portrait, particularly the face, during sittings, completing the costume and background subsequently. In this case, there is technical evidence which suggests that Romney rushed the completion of the picture, and changed his mind about painting in the sitter’s right arm, presumably in response to the Trotters’ demands that the portrait be completed. (http://www.tate.org.uk/art/artworks/romney-mrs-robert-trotter-of-bush-n02943)