Prince Philip dead at 99: Queen announces with 'deep sorrow' that husband the Duke of Edinburgh 'passed away peacefully at Windsor Castle' this morning - three weeks after he finished 28-night hospital stay for infection and heart surgery Her Majesty announced death of her husband of 73 years at midday today and joins 'the world in mourning' Philip was in Windsor after being treated for an infection and pre-existing heart condition for 28 nights Duke of Edinburgh had kept a low profile since conducting his final solo public engagement in August 2017 After retiring, Philip spent much of his time at Windsor and at Queen's private Sandringham estate in Norfolk