Nobody ever knows for sure how much royals such as Edoardo Mapelli Mozzi and Prince Harry spent on their wives' engagement rings.
However, we've turned to the expertise of Jewellers Est 1897 and other engagement ring specialists to find out the possible prices of the Princess of Wales' inherited sapphire, Princess Anne's two rocks, and Queen Camilla's heirloom.
So which royal bride has the most expensive rock? Find out…
Back in May 1973, the Queen's daughter was given a sapphire and diamond ring by Captain Mark Phillips. The couple got married in November 1973 before getting divorced in 1992.
Anne later married Vice Admiral Sir Timothy Laurence in 1992 after he popped the question with a vintage ring featuring an oval cabochon sapphire that is flanked by diamonds.
Engagement ring specialist Max Stone at Seven Stone estimated her first jewel was worth around £10,000, while her second is valued at £25,000.
Prince Andrew proposed to Sarah Ferguson in 1986 with a rare Burmese ruby surrounded by ten glittering diamonds, which was reportedly inspired by Sarah's fiery hair. The stones form a flower pattern, much like her daughter Princess Eugenie's ring.
At the time, Sarah's beloved ring cost around £25,000, but inflation and the sentimental backstory mean it could be valued in the region of £70,000.
When Edoardo Mapelli Mozzi popped the question to Princess Beatrice, he presented the royal with a stunning 3.5-carat gem with a reported cost of £78,000. Edoardo worked with Shaun Leane to design Princess Beatrice's dream ring, in a process the jewellery designer told HELLO! took four months. "He knew he wanted a modern classic," Shaun revealed.
Queen Camilla was given a beautiful art deco ring by King Charles III and it features a five-carat emerald-cut diamond in the centre, with three diamond baguettes on each side. It once belonged to the Queen Mother, Charles' grandmother, and it has a value of £100,000.
Duchess Meghan's dazzling trilogy ring boasts a large central diamond which Prince Harry sourced in Botswana and it is flanked on either side by two smaller jewels which are from his late mother Princess Diana's personal collection. Her incredible five-carat gem is thought to be worth £134,500.
Zara Tindall's stunning ring from her husband Mike features a single solitaire diamond on a split platinum band with several pavé set diamonds. It is thought that the low-sitting diamond was specially selected because of Zara's keen sporting career, so it wouldn't get in the way at equestrian events. Mike Fried, CEO of The Diamond Pro, puts the ring's value at around £140,000.
No doubt one of the most famous royal engagement rings of all time, Diana, Princess of Wales selected her own dazzling sapphire ring when she got engaged to then-Prince Charles, and it has since gone down in history. The amazing 12-carat, oval-cut jewel is estimated to be worth £390,000.
Princess of Wales
As Princess Kate's engagement ring from Prince William was inherited from Princess Diana, it has the same price tag of £390,000, however, it is believed that with this unique legacy, the precious jewel would almost certainly be worth much more now.