Prince Charles, his wife Camilla, Prince William and his wife Kate the Duchess of Cambridge made a rare joint appearance at the premiere.
The comments come as Buckingham Palace struggles to combat suggestions of racism raised by Prince Harry and Meghan.
Prince Harry, who marries US former actress Meghan Markle on May 19, has been transformed in recent years from an angry young man into one of the British royal family's greatest assets.
An avalanche of royal documentaries is set to flood schedules across the world in the run-up to the marriage of Britain's Prince Harry and the American actress Meghan Markle next month.
Being a royal a full-time job? Actress Meghan Markle quits 'Suits'; ditches career after engagement to Prince Harry
Meghan Markle played Rachel Zane in the 'Suits' series, which she has been associated with for seven years. Will having a working actress be too modernizing a reform for the British royal family?