Meghan Markle was denied her favourite tiara days leading up to her wedding.
The Suits star, who married into the royal family in 2018, wanted to wear a Russian head piece on her big day, but the Queen rejected her plea due to the ornament's 'sensitive origin.'
Speaking to Palace Confidential, Mr Richard Eden said: "It's not just the Koh-i-Noor, honestly, because of the colonial, sort of, the legacy of the Royal Family, there are stories behind so many different jewels.
"There was one tiara that, I think, Meghan had expressed an interest in wearing.
"Then it was pointed out that there were Russian connections, which were all a bit awkward."
He added: "Then it was decided that she wouldn't wear that one.
Earlier in his book, royal author Robert Lacey claimed: "We were told that the Queen felt that she had to say 'no' to Meghan's first choice, a beautiful emerald headdress that was said 'to have come from Russia'".
He added that "this was code for a sensitive origin".
He continued: "The treasure was one of those that had found its way into Windsors' hands through 'undefined' not to say dodgy channels - and for an undisclosed price - in the aftermath of the Russian Revolution.