Richard Fitzwilliams said despite the humiliation that Sarah Ferguson, royally known as Fergie, had taken over from the royal family, the queen would not have to give up consent to Prince Andrew's wedding. He also discovered that a couple would not have to seek approval from Andrew's father Prince Philip, who does not like Sarah because he is retired.
He told Express.co.uk: "Yorks are a close family. Despite divorce in 1996, Andrew and Sarah are still the best friends
"The Queen would not have to give his consent, and Prince Philip, who disdained, withdrew."
But Fitzwilliams said "strongly suspect" Prince Charles would welcome the gathering.
Fergie and Prince Andrew sparked speculation that they reunited after being recently seen at the Royal Ascot and they came together to the wedding of Lady Gabriella Windsor.
And the Duchess of Yorka recently shrieked over his former wife and relationships shared by Princess Beatrice and Princess Eugenie's parents.
Sarah said Hello! "We work in unity, Andrew and I are focused on being good parents together. We're bigger than friends."
And in April it was claimed that Yorks were "friends with privileges".
Speaking of ITV Lorraine, journalist Dan Wootton said, "They are currently in touch with" benefiting friends ".
Mr. Fitzwilliams said that Sarah would be "delightful" that would be welcome back to the royal crowd after years of being left in the cold.
He said, "There is no doubt that Sarah is delighted that Queen of Balmoral has been back in 2013 and Royal Ascot.
"Their recent marriage to Eugenie with Jack Brooksbank was sensationally successful and made for excellent television."
But a royal expert said he believed the couple should not marry again because he "just does not match the royal role".
The couple remained gloriously imprisoned since the divorce in 1996 after 10 years of marriage and even shared their residence.
In 1992, the Duke and Duchess of Yorka finally announced their separation after spending a lot of time while Prince Andrew was on royal duties.
Just a couple of months later, photos of dwarves came from the oil tycoon John Bryan, who was described as her financial advisor, and a couple divorced in 1996.