http://en.wikipedia.org/wiki/Alice_Keppel

Alice Frederica Keppel, née Edmonstone (29 April 1868 – 11 September 1947) was a British society hostess and a long-time mistress of King Edward VII.

Both she and her husband, The Honourable George Keppel, came from aristocratic backgrounds, but were almost penniless, and they both agreed that she must cultivate rich lovers to maintain their upper-class lifestyle. Alice performed this role with a charm and discretion that much impressed London society and soon brought her to the attention of the future king, whose mistress she remained till his death, lightening the dark moods of his later years. The Queen even allowed her to visit him as he was dying. But his death instantly reduced her social status, and she thought it more dignified to live abroad.

Her daughter was the writer Violet Trefusis. Alice's great-grand-daughter is Camilla, Duchess of Cornwall, second wife of Charles, Prince of Wales.