Princess Kate and Prince William made a decisive move to separate from Meghan Markle and Prince Harry, according to James Holt.
Holt is the executive director at Meghan Markle and Prince Harry's Archewell organisation.
He previously worked as the Head of Communications for the Royal Foundation.
Holt told Netflix's documentary on the Sussexes that Kate and William's annual Christmas party splitting into two parties in 2018 was the moment he realised the separation was happening.
Prince William and Kate have reportedly not spoken to Prince Harry since Queen Elizabeth II's funeral in September 2022.
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He said: "Every year Kensington Palace hosts a Christmas party for the principals and the staff.
"And so we were gearing for one big party and very shortly before the party, it became two parties."
He added: “Actually that was the point that you realised that these offices are separating."
King Charles is understood to be the only senior member of the Royal Family who is speaking to the Duke and Duchess of Sussex.
However, Princess Kate and Prince William will tolerate Prince Harry at the Coronation according to a royal commentator.
Kinsey Schofield said that Kate and William would have had a harder time dealing with Meghan Markle, had the Duchess of Sussex also come to the Coronation.
She told Fox News Digital: "Both William and Catherine will tolerate Harry's presence because, despite the bad blood and betrayal, there is a deep love for him in both of them.
Princess Kate and Prince William will tolerate Prince Harry at the Coronation according to a royal commentator.
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"The same could not be said for Meghan. I think William and Catherine would have had a much harder time navigating that.
"I do not anticipate warm interactions between Harry and his older brother.
"We know that Palace staff is planning every entry, exit and seat with the battling brothers in mind.
"The Palace's ultimate objective is to avoid conflict."