James Macardell, Mary, Duchess of Ancaster, mezzotint after a painting by Thomas Hudson

Mary Panton, illegitimate daughter of Thomas Panton, Master of the King's running horses at Newmarket, married Peregrine Bertie, 3rd Duke of Ancaster in 1750. Their London home was in Berkeley Square. She was a leader of fashion and in 1761 was appointed Mistress of the Robes to the young Queen Charlotte.The Duchess is shown here dressed as if for a masquerade at Ranelagh - the amphitheatre is in the background - wearing a variation of the fashionable 'Van Dyck dress' in which artists had portrayed sitters since the 1730s. The feathered hat and fan, the puffed sleeves and the arrangement of the skirt pinned up at the sides are all taken from the costume worn in a portrait then thought to show Helena Fourment and to be by Van Dyck (it is now identified as Susanna Fourment and attributed to Rubens), but the seventeenth-century ruff has been reinterpreted so that it is merely hinted at in the lace around the Duchess's neck.Fourment's costume was often repeated as a formula by specialist drapery painters, who would never see the sitter. Here, however, the treatment is unusually convincing. It is possible that the Duchess actually had such a costume made for a masquerade at Ranelagh. In 1742 Horace Walpole described seeing at a masquerade given by the Duchess of Norfolk: 'quantities of pretty Vandykes, and all kinds of old pictures walked out of their frames'.