The Queen wearing the Cartier Diamond Rose Clip BroochFor Day 2 of Royal Ascot 2016, The Queen debuted a new brooch! It was described by the palace as a "Cartier diamond flower clip." The jewel features a large round diamond at its center, surrounded by six slightly smaller round diamonds and set inside a group of curving petals. It is a match to this brooch:
I do not believe this has been seen on any previous royal woman, so we could be looking at a new addition to the collection as well as a public debut for The Queen; it is worth noting, though, that King George VI and Queen Elizabeth were collecting many pieces from Cartier in that timeframe. It's an absolutely lovely design, and certainly seems suited to The Queen's taste. She has many other floral brooches, of course, and also plenty of Cartier designs, such as the Nizam of Hyderabad Rose Brooches and the Williamson Diamond Brooch.
15 June 2016: Royal Ascot, Day 2