The Diamond Diadem is arguably The Queen of England’s most recognizable piece of jewelry. As immortalized here in Cecil Beaton’s coronation portrait, Elizabeth II first wore the ornamental headpiece—it is a tiara, not a crown—to her first State Opening of Parliament in 1952 and has worn it to state openings every year since.  “The piece is an incredibly important part of the British royal collection,” says Ella Kay, editor of the blog The Court Jeweller. “The Windsors have almost no important jewelry that predates the 19th century—in part because Queen Victoria lost quite a few pieces to her Hanoverian relatives in a lawsuit. It’s one of the very oldest pieces that the queen wears on a regular basis.”  The headpiece is set with 1,333 brilliant-cut diamonds, a 4 ct. pale yellow brilliant, and 169 pearls in silver and gold. Originally, it was made in 192