In 1947, just before she announced her engagement, the then-Princess Elizabeth went on a tour of South Africa with her parents and her sister. She celebrated her twenty-first birthday during the trip, and she received a pretty impressive birthday gift: diamonds!
At the end of a ball held on her birthday at Government House in Cape Town, South African prime minister Jan Smuts presented the princess with a diamond necklace made by Garrard. It featured twenty-one large brilliants, one for each of her twenty-one years, interspersed with smaller baguettes and brilliant stones, set in platinum. The largest diamond in the necklace weighs ten carats.
Hugh Roberts notes that the princess let out "unaffected exclamations of delight" when she was presented with the necklace. The present was improved upon even more when a detachable snap closure was added, using a six-carat diamond that had been given to Elizabeth three days before her birthday by Sir Ernest Oppenheimer, the chairman of De Beers.
In 1952, Garrard revised the necklace, shortening the piece. Five of the large brilliants were removed, as was the De Beers snap closure. Those stones were used by the jeweler to construct a bracelet to match the necklace. The necklace is now 40.5 centimeters long, and the bracelet measures 17 centimeters in length.
Even though they're among the oldest pieces in her personal jewel collection, HM still wears the South African diamonds today.
They were an especially appropriate choice for the South African state visit to Britain in 2010, where she wore them at the state banquet.