Lady Sonia, the widow of former Australian prime minister Sir William McMahon, was regarded as a elegant socialite and generous patron. She was connnected to a number of charity organisations including the Sydney Children's Hospital Foundation and the Australian Cancer Research Foundation. In 1971 during an official visit to the White House, she made international headlines when she wore a daring white dress split up to the armpits on both sides and held together by rhinestones. Lady Sonia's health declined in more recent years when she was seriously injured in a fall on a yacht in 2009 and had battled cancer. She is survived by her three children.