Ursula, Lady Westbury, who has died aged 99, was the Superintendent-in-Chief of St John Ambulance who organised a party for more than 100,000 children in Hyde Park featuring a nine-mile-long sausage; a lifelong friend of both Queen Elizabeth II and Princess Margaret, she took on informal royal duties including representing Princess Margaret at memorial services and chaperoning the 23-year-old Prince Andrew on a trip to New York.