Born on 13 November 1785 in London, Caroline Ponsonby was the third child and only daughter of Frederick Ponsonby, third Earl of Bessborough, and his wife, the former Lady Henrietta Frances Spencer. During her life Caroline inhabited the households of three aristocratic families. From age nine she lived with her maternal aunt, Georgiana, Duchess of Devonshire, at Devonshire House. Adjacent to Hyde Park, this mansion and its grounds dominated a huge area between Berkeley and Stratton Streets in Piccadilly. Described by Elizabeth Jenkins, Caroline Lamb's first biographer, as "the very temple of Society, frequented by a 'gorgeous train' headed by the Regent, Fox, and Sheridan," Devonshire House embodied the political and social power of eighteenth-century Whig aristocracy. Caroline's father, Frederick, was a Whig statesman and politician, her mother, Henrietta, a social virtuoso, adroit at the politics of Whig society. John Spencer, Caroline's maternal grandfather, held four peerages as a Whig...