Princess Alexandra, our Magpie of the Month, prefers to wear choker necklaces that sit close to the throat. You'll see her most often wearing a pearl choker with a diamond-shaped clasp, but she does have other necklaces in her collection, including today's piece.
The necklace is intricate and appears to be primarily set with diamonds, though good close-ups are elusive; from some angles, I think I can see pearls in the setting as well. (That is, of course, if it's not costume jewelry -- but Alexandra's pieces mainly seem to be the real deal.) To my knowledge, this necklace hasn't been discussed much, and I don't know its provenance. However, I do know that photographs show Alexandra wearing it for at least the past twenty years. The image at the top of this post shows her wearing the necklace at a gala event in January 1995.
The choker has made appearances at some big family milestone events for the Windsors. She selected the necklace for the 70th birthday party for her brother, the Duke of Kent, in 2005, and a year later, she wore the same necklace to the Ritz for the Queen's 80th birthday party. Choker necklaces aren't always easy to wear, but on elegant Alexandra, this one's a winner for me.