The expert suggested the piece could be worth as much as £35,000, with others valuing the jewel at £100,000.
Prince Edward purchased the engagement ring from Garrard, a jewel which is steeped in royal tradition.
Garrard was the crown jeweller for many years and has produced various items for the Royal Family.
It also created the sapphire and diamond engagement ring which once belonged to Princess Diana and is now worn by Kate Middleton.
As well as making a nod to other royal jewels, Sophie’s diamond has some notable similarities to Meghan Markle’s engagement ring.
The expert continued: “This style of engagement ring is known as a trilogy ring.
“Traditionally the three central diamonds are said to represent the couple’s past, present and future, making it a very romantic and meaningful choice of design.”
When Prince Harry proposed to the Duchess of Sussex, she was given a custom ring which also featured a trinity design.
“It has helped to revive the desire for the trilogy look. The growing popularity of the trilogy engagement ring was a distinctly growing trend for 2020 and I believe it will continue to be a popular choice in 2021.”
The engagements rings worn by Sophie and Meghan both have a similar design.
Sophie and Prince Edward tied the knot at Windsor Castle on June 19, 1999.
On her wedding day, Sophie was given a Welsh gold wedding band in line with royal tradition.
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The royal line of succession – who outranks who?
The line of succession to the British throne dictates the order in which each member of the Royal Family would ascend to the throne.
It is also seen as a ranking of importance with the head of the line, the Queen, taking the place of ruler.
Older children come before younger children. Traditionally boys came before girls, but this law was changed on 26 March 2015 before the birth of Prince William’s first child.
Incredibly, Catholics are still excluded from the line of succession, as are children born outside of wedlock.
The royals, who usually stick to a strict protocol when appearing in public, often arrive at events in ascending order of importance, with the most important royal arriving last.
Prince Charles, 72, is currently first-in-line to the British throne, followed by Prince William, 38, his oldest son.
Then comes Prince William’s children, George, seven, Charlotte, five, and Louis, two, and they are followed by Prince Harry, 36. Prince Harry is succeeded by his son Archie Harrison, born in May 2019.