Prince William (C), the Duke of Cambridge, and his wife Catherine, the Duchess of Cambridge and Prince Harry arrive at the White Garden in the grounds of Kensington Palace in London, Britain on Aug. 30, 2017 to commemorate the 20th anniversary of the death of Princess Diana. (Xinhua)

Prince William (L), the Duke of Cambridge, and Prince Harry lay flowers in Kensington Palace to commemorate the 20th anniversary of the death of Princess Diana in London, Britain on Aug. 30, 2017. (Xinhua)

Prince William (R), the Duke of Cambridge, and Prince Harry lay flowers in Kensington Palace to commemorate the 20th anniversary of the death of Princess Diana in London, Britain on Aug. 30, 2017. (Xinhua)

Prince William (C), the Duke of Cambridge, and his wife Catherine, the Duchess of Cambridge and Prince Harry arrive at the White Garden in the grounds of Kensington Palace in London, Britain on Aug. 30, 2017 to commemorate the 20th anniversary of the death of Princess Diana. (Xinhua)