[2] On 29 January 1756, Anne married Augustus Henry FitzRoy, Earl of Euston, at her father's house in St James's Square, by special licence of the Archbishop of Canterbury, as she was 18 and considered a minor.

In 1764, while the Duchess was pregnant with their second son, Grafton began a public affair with former prostitute Anne Parsons, whom he brought without shame to the Royal Opera.

[7] In 1766, Walpole introduced her to an Anglo-Irish peer he had met in Paris, John FitzPatrick, 2nd Earl of Upper Ossory, whom he called "one of the prosperest and most amiable young men I ever knew".

[7] Meanwhile, the Duke was gradually assuming control of the government during Earl of Chatham's illness and death, and in October 1768 he effectively became the first Prime Minister, as Head of Ministry.

[9] Elizabeth was ironically Ossory's cousin, the daughter of his aunt Lady Mary Leveson-Gower and Sir Richard Wrottesley, 7th Baronet, the Dean of Worcester.

[11][12] Though the marriage legitimised their daughter, the Ossorys still found themselves exiled from much of London's social scene, as divorced women were not allowed at the Royal Court of George III.

Additionally, Grafton was now the most powerful man in Westminster, even flaunting his mistress in public before Charlotte of Mecklenburg-Strelitz at the Royal Opera House.

In the first year of their marriage, Charles Douglas, 3rd Duke of Queensberry visited Ampthill wrote George Selwyn that the Ossorys "live but a dull life, and there must be a great deal of love on both sides not to tire".