It's time for a British royal tiara showdown!Everett Collection Inc/Alamy, Getty ImagesThe Ogilvy Tiara vs. The Poltimore TiaraEverett Collection Inc/AlamyThe Ogilvy TiaraSir Angus Ogilvy commissioned this diamond floral sparkler for his new wife, Princess Alexandra of Kent, in the early 1960s. Collingwood made the tiara using a set of diamond flowers that have interchangeable center stones,