It seems that Sarah Ferguson regularly attends this Amfar gala. In 2011, she attended the gala, wearing a diamond necklace that she had received and regularly worn when Duchess of York:
Sarah Ferguson, Duchess of York attends amfAR's Cinema Against AIDS Gala during the 64th Annual Cannes Film Festival at Hotel Du Cap on May 19, 2011 in Antibes, France. (Credit: François Durand/Getty Images Europe)
26 May, 1987: gala dinner at the Claridge's Hotel, during King Fahd of Saudi Arabia's State visit to the United Kingdom: