Queen Elizabeth, Kate Middleton, Princess Diana, and Meghan Markle. Who has the most expensive engagement ring?

With Meghan Markle and Princess Eugenie getting engaged within two months of each other, people have been comparing the values of their engagement rings and this has led to people wondering who among the British royals owns the most expensive engagement ring.
With regards to that, Queen Elizabeth II, Princess Diana, Meghan Markle, Kate Middleton and Princess Eugenie's engagement rings were compared in value. Check out whose royal engagement ring is the priciest, according to Metro.

Queen Elizabeth II
The queen's engagement ring is personally designed by Prince Philip with the help of jeweler Philip Antrobus Ltd. The band features a 3 carat "old cut" diamond set in a claw setting in platinum.
The diamond was taken from a tiara that belongs to Prince Philip's mother, Princess Alice of Greece. The ring is estimated to cost $284,168.
Princess Diana and Kate Middleton
Prince Charles gave Princess Diana a sapphire engagement ring from Garrard & Co Ltd. It was not custom-made like the other royal rings. It features 14 solitaire diamonds surrounded by Sri Lankan 12-carat oval faceted blue Ceylon sapphire and was set in 18-carat white gold.
Later on, Prince William used the same ring when he proposed to Middleton. In 1981, the ring was valued at $39,784. But at the time it is estimated to have an insurance value of $426,252.
Meghan Markle
There are different opinions when it comes to the value of the "Suits" star's engagement ring. According to Deborah Papas, a gemologist from Prestige Pawnbrokers, it has an estimated value of $70,000. However, another gem expert claimed that Prince Harry's engagement ring to Markle is worth $174, 218.
"From seeing the pictures, I would estimate that the centre diamond is a slightly elongated cushion cut diamond, approximately 3.00 - 4.00 carats. The side diamonds are more than likely oval or round cut diamonds about 0.75 carats each," the expert explained. "We would estimate that the value of the centre stone would be around £70,000 - £115,000 ($99,553 - $163,552), while the side stones would have an intrinsic value of around £3,750 ($5,333) each."
Princess Eugenie
Meanwhile, Papas claimed that Princess Eugenie's engagement ring is estimated to cost over $140,000. The pink padparadscha sapphire ring surrounded by diamonds includes "the rarest and most valuable of all the corundum varieties."
Initially, Papas said that Princess Eugenie's ring is twice the cost of Markle's band, which is priced at $70,000. But another expert said that Markle's ring is worth over $170,000. If the second gemologist is correct, then the "Horrible Bosses" star's ring is more expensive.

However, neither Markle nor Princess Eugenie owns the most expensive ring. That one belongs to Princess Diana and Middleton, who share the same band.