Buckingham Palace says Queen Elizabeth II, Britain's longest-reigning monarch, has died. She was 96. Elizabeth spent more than seven decades on the throne as the U.K. rebuilt from war, lost an empire, transformed its economy and both entered and left the European Union. She was a constant presence, the only monarch most Britons have ever known, and she guided the institution of the monarchy through choppy waters. She likely met more people than anyone in history, and her image, which adorned stamps, coins and bank notes, was among the most reproduced in the world. But her inner life and opinions remained largely an enigma. The impact of her loss will be huge, and unpredictable.