5. No Hats for Women in the Evening

Reason: Overly casual
Exception: None Royal ladies are expected to wear hats to formal events throughout the day, but they should not be worn during the event itself because they are too casual and, anyway, who needs to wear a hat when it’s not sunny outside?
No Hats for Women in the Evening ©Anwar Hussein via Getty Pictures
If you’re a married woman, the tiaras come out after 6 p.m. Every royal owns a tiara; these items are much more effective at creating a statement at evening dinners, galas, and balls than caps.