One of my favorite brooches from the jewelry collection of Queen Elizabeth is undoubtedly the Jardine Star Brooch. Symmetry, diamonds, mystery: this brooch has it all!
Our best source of information about the history of this brooch is Leslie Field's The Queen's Jewels. (Curiously, even though HM chose to wear the Jardine Star during her Diamond Jubilee weekend in 2012, it wasn't discussed in any of the three jewelry books -- Roberts's The Queen's Diamonds, de Guitaut's Diamonds: A Jubilee Celebration, or Kelly's Dressing the Queen -- published in connection with the big anniversary.)
Here's what Field tells us about the brooch: "In 1981 the Queen was left a late-Victorian diamond star brooch by Lady Jardine, which she has worn on many occasions. It has a collet diamond on a knife-wire between each of its eight points." No information is given regarding the maker of the brooch.
Who exactly was Lady Jardine? It's not exactly clear. There's a Clan Jardine in Scotland, though to my knowledge, none of the wives of the baronets of that clan died in 1981. There are also miscellaneous other people in the twentieth century who have Jardine baronetcies, but again, none of their wives appeared to have died in 1981. Did Field make an error on the date? Is Lady Jardine even real? Verdict's out. Her identity remains a bit of a mystery.
The Queen's affection for this brooch, however, isn't mysterious at all. She wears the piece very regularly, including at high-profile appearances like holiday church services, Christmas broadcasts, and the aforementioned Diamond Jubilee water pageant. I can't blame her at all: this brooch is absolutely lovely and classic, and the fact that it's an all-diamond piece means that it can be coordinated with a large number of outfits.