Michael Dahl (1659-1743)

As the only surviving child of Edward Harley (1689-1741), later 2nd Earl of Oxford, and his wife Henrietta Cavendish Harley (1694-1755), only daughter of John Holles (1662-1711), Duke of Newcastle upon Tyne, the sitter was one of the most eligible heiresses of her generation. To her marriage to William Bentinck (1709-1762), 2nd Duke of Portland, in July 1734, Margaret brought a dowry of £20,000, along with the estates of Welbeck Abbey, Nottinghamshire, and the valuable London property centred upon Cavendish Square. The couple's son and heir, William Henry Cavendish (b.1738), 3rd Duke of Portland, was a distinguished statesman during the reign of King George III and was twice Prime Minister (in 1783 and 1807).

A favourite of the literary circles that surrounded the Harleys, Margaret was addressed in a poem by Matthew Prior as 'My noble, lovely, little Peggy' at the age of five. At the age of eight, she was portrayed as a shepherdess in a portrait by Dahl (Welbeck Abbey). She became a passionate collector of natural history specimens and a patron of the arts and sciences, and was buried at Westminster Abbey.

The families of Portland and Kinnoull were linked through the marriage of the 8th Earl of Kinnoull on 1 September 1709 to Abigail (d.1750), youngest daughter of 1st Earl of Oxford, Lord High Treasurer of Great Britain.