There have long been rumors that royal sister-in-laws Meghan Markle and Kate Middleton have been engaging in a longstanding feud. Now, royal insiders are revealing the origins behind this feud for the first time in a book that is sure to reveal many secrets of the British royal family.

Tom Quinn sat down with various royal insiders for his new book “Kensington Palace: An Intimate Memoir From Queen Mary to Meghan Markle,” and some of the most interesting pieces of information he found was about the feud between the wives of Prince William and Prince Harry.

“Kate is actually one of the nicest royals, and she hasn’t let life in her extremely grand apartment at Kensington go to her head — or at least not too much,” one palace insider said, according to Daily Mail. “She is nice to her staff, in the main, and she was very warm towards Meghan when she arrived.”

“But tensions were bound to arise because Meghan inevitably had to accept that, although she is a duchess, she is not married to the next king,” the source added. “I think she has found that difficult to deal with.”

Another former palace servant revealed what really started the feud between the two women.

“Kate was horrified when Meghan shouted at a member of Kate’s staff — that was definitely the beginning of discussions about leaving Kensington Palace,” the ex-servant explained. “Like many people not used to dealing with servants, Meghan overdoes the imperiousness; so on the one hand she wants to be like Diana, a people’s princess, and on the other she wants people to stand to attention when she clicks her fingers.”

Meghan reportedly quickly earned a reputation among staffers for being demanding, and they soon gave her nicknames like “Me-Gain,” the “Duchess of Difficult” and even “Di 2” or “Di Lite.”

The rift between the royal couples seems to be greater than ever these days, as Harry and Meghan have stepped down as senior members of the British royal family and moved to her hometown of Los Angeles, California. William and Kate, however, are still in the United Kingdom, where they are likely to remain as William is set to eventually take the British throne.