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With Royal watchers speculating that Prince William will soon propose to girlfriend Kate Middleton, the next thing everyone wants to know after when it will happen is who will design the engagement ring? The odds-on favorite is Garrard, jeweler by appointment to the Crown (Diana and Fergie’s rings both came from the British institution). What kind of design will Wills choose for his bride-to-be? We predict the classic but fashionable Middleton will like an elegant square shape—like an Asscher or a cushion-cut—in a beautiful platinum and diamond boxter setting.

Until Prince William pops the question to Kate Middleton, here’s a look at the most memorable royal engagement rings from over the years.

—Marion Fasel