Kate Middleton wears Princess Diana's tiara at state banquet

• Kate Middleton wore Princess Diana's famous tiara at a state banquet.
• The event took place on Oct. 20 in the U.K.
• The banquet was to honor Sultan Haitham bin Tarik of Oman.
• Kate Middleton wore a yellow keyhole gown.
• This tiara has become a signature piece for Kate Middleton at formal events.