Sarah Ferguson, the Duchess of York, 58, married her ex-husband Prince Andrew in 1986.
The redhead from London was presented with a stunning Burmese ruby when Andrew proposed on March 19.
The third child of Queen Elizabeth II proposed at Floors Castle in Scotland.
The couple met when they were children, but Princess Diana introduced Sarah Ferguson and Prince Andrew in later years.
Princess Diana played cupid at a party at Windsor Castle held after the Ascot Races, and Sarah and Andrew hit it off straight away.
Prince Andrew chose a ring much like Fergie’s friend Diana’s, with a colourful stone surrounded by 10 diamonds on a yellow gold band.
The ring was created by Garrard, which also created Diana’s engagement ring.
While the total cost of the ring is not known it can be assumed the price tag was rather hefty thanks to the costly centre stone.
According to Hello! the Burmese ruby chosen by Andrew to represent Fergie’s red hair cost him a whopping £25,000.
Given inflation, the same stone would cost £71,350 today.
And of course, the royal association is bound increase the price tag of such a piece today.
You won’t believe how much Princess Diana’s engagement ring is worth now.
Kate Middleton now wears the ring after she was given the jewel by her husband Prince William when he proposed in 2010.
The ring was originally bought for Lady Diana Spencer in 1981, and cost an eye-watering £28,500.
How much is Meghan Markle’s engagement ring worth?
Meghan Markle’s engagement ring from Prince Harry is a stunning piece with three diamonds and a gold band – which the Prince revealed is Meghan’s favourite metal.
The huge central stone is a new purchase, while the two diamonds either side belonged to Princess Diana, and are from her private jewellery collection.