AceShowbiz - One of the reasons why Meghan Markle won't be attending King Charles' coronation is probably Princess Kate Middleton. A royal expert claims that the Princess of Wales prevented the Duchess of Sussex from joining her husband Prince Harry at the event which is set to take place at Westminster Abbey on May 6.

"We must all be grateful that Kate, in the end I think, prevented Meghan from coming and said she 'wouldn't have her there under any circumstances,' " former BBC journalist Tom Bower said on GB News on Wednesday, April 12.

According to Tom, the wife of Prince William gave the former "Suits" actress a warning. "If she [Meghan] did come, she'd have to sit at the back," Tom said of the alleged warning.

Meanwhile, Tom noted that "Harry's presence is constitutionally important." The "Revenge: Meghan, Harry and the War Between the Windsors" author explained, "After all, God forbid something happens to [Prince William and his children, Prince George, Princess Charlotte, and Prince Louis], and all of them died - we'd have King Harry on the throne after Charles, so he's got to be there."

Tom, however, noted that Harry won't likely join the working members of the royal family on the Buckingham Palace balcony. "If he let Harry come on the balcony, he'd have to have Prince Andrew on the balcony and to have two renegade princes in front of the public like that would be a very bad start to King Charles' reign," the royal expert continued.

On Wednesday, Buckingham palace and representatives for the Duke and Duchess of Sussex confirmed that Harry would attend the historic event alone, without his wife. "Buckingham Palace is pleased to confirm that The Duke of Sussex will attend the Coronation Service at Westminster Abbey on 6th May," Buckingham Palace said in a statement. "The Duchess of Sussex will remain in California with Prince Archie and Princess Lilibet."

While Harry will jet off to the U.K., Meghan will stay in California to celebrate Prince Archie's fourth birthday which happens to fall on May 6 as well. On the other hand, a source revealed Meghan won't join Harry at the coronation at Westminster Abbey because things still remain "awkward" between Meghan and the royal family. "There was no way that Meghan was going to miss her son's birthday," the source told Page Six.

"They had to make a decision that felt genuine and authentic, especially after everything that has been said and all the things that have gone down," an insider familiar with the Sussexes told Page Six.

However, even with Meghan's absence, things may still be awkward as the coronation visit marks the first time for Harry to see his family since making a series of bombshell accusations in his book, "Spare". The royal insider shared, "Even though Meghan is not going, it's still going to be extremely awkward."