The possible subject of this portrait is Margaret Bentinck (born Cavendish-Harley), who was a great collector of fine art and natural history. Her collection included the celebrated Portland Vase, now in the British Museum. Christian Friedrich Zincke (about 1683–1767) arrived in England in 1706 to work for Charles Boit. He eventually set up his own studio and became the most successful enamel painter of his time. Commissioning work from Zincke was immensely fashionable, and demand was such that his studio trained other enamellers who later found success of their own.

In the 17th century, new techniques of painting enamels allowed delicate portraits resembling tiny oil paintings to be created. These enamel miniatures were first fashionable in continental Europe, but were particularly in vogue in Britain from the 1720s to 1760s. Painted enamels were made by firing finely milled glass which had been coloured with metal oxides onto a metal base, usually gold or copper. The colours had to be applied and fired in several stages, according to the firing temperature required by each colour. Incredible precision was needed for a successful enamel portrait, since each firing carried risks of cracks and bubbles that might ruin the entire effort.

Sir Arthur Gilbert and his wife Rosalinde formed one of the world’s great decorative art collections, including silver, mosaics, enamelled portrait miniatures and gold boxes. Arthur Gilbert donated his extraordinary collection to Britain in 1996.