She said: “If you think about royal style, it’s very singular in its power and purpose. There are very few people who what they wear gets so much attention.
“This started back with Kate a decade ago when she married Will and it took all of the interest which started with Diana and it added a shopping element to it.
“There are people who can identify, not just the dress, but the earrings, the shows and the hats…
“Kate did this beautifully as she was relatable. She shopped off the rack, she bought pieces you could buy.
“Suddenly if you saw Kate in a dress, you could buy and wear, there lies some affection and Kate has continued this for the last decade.
“Meghan knew it very well when she entered the Royal Family. She knew how to dress to send a message and she picked her brands very carefully.”
The expert suggested both royals are mindful when picking brands as they know how the demand is likely to grow for the retailer.
While the outfits worn by Kate and Meghan have a similar effect on royal fans, Elizabeth suggested the Duchesses have different styles.
“Here is Meghan, a modern woman and accomplished actress entering into the conversation, including the royal style conversation, and doing things different, doing things her way.
“That was tremendously exciting and I think a lot of people started to pay attention to the Royal Family because they saw something that interested them in Meghan.”
She added the attention around Kate and Meghan’s style is unlikely to change regardless of their royal roles.
Elizabeth concluded: “I don’t know if the Oprah special changes any of that. There are Kate fans who will forever shop what Kate wears and Meghan fans who will forever shop what Meghan wears.”
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.