There’s nothing more English than a beautiful garden, and no one more English than Princess Diana. So that’s where Prince William and Prince Harry chose to pay tribute to their mother on Wednesday, the eve of the 20th anniversary of her death. Clutching umbrellas, the princes and Duchess Kate of Cambridge, William’s wife, visited the Sunken Garden on the grounds of Kensington Palace — their current central London residence and Diana’s former home. The engagement was to be the young royals’ sole public appearance before the anniversary, aimed at highlighting their mother’s life and her charitable legacy. They were expected to spend the anniversary day in private.