Prince Harry and Meghan Markle unexpectedly referred to their daughter Lilibet as "Princess" in a statement confirming her christening last week.

However, although the Sussex couple's representatives insisted that this was in agreement with Prince Charles and that the children should be called Prince Archie and Princess Lilibet, a source now says that the royal family feels "caught off guard" by the move.

The source told OK! that after the Queen's death, Harry had a "casual conversation" with his father, the King, but they did not reach the agreement that the Sussexes claim.

The royal couple previously said in a statement, "Since my grandfather became monarch, the titles of our children have been their birthright. This issue has been settled for some time, in agreement with Buckingham Palace."

The royal couple also said in a statement that "the royal family has been in agreement with Buckingham Palace for some time.

Shortly after this statement was issued, the royal court said it would update the names of the children in the line of succession "in due course," but that was within hours.

However, if OK!'s sources are to be believed, the King feels his hand has been forced by Harry and Meghan's decision to call their daughter "Princess Lilibet" in a public statement.

"King Charles feels railroaded," the source said. 'As far as he knows, the title issue was still unresolved.'

Lili was christened last Friday in Los Angeles, but none of the UK-based royals attended.

"They [the royal family] knew the christening was going to take place, but due to work commitments they could not attend. They were invited at the last minute," the source said.

"They didn't expect the title to be used in an official setting."

Commentators have previously supported the idea that the royal family skipped the christening not to belittle the Sussexes, but because of their packed schedule.

"The royal schedule is planned more than a year in advance to accommodate official events and to support the vast number of charities that visit each year. And then there is the small matter of planning the coronation," royal historian Mok O'Keefe previously told "Marie Claire."

"The royal family has a long history of planning coronation ceremonies,"

and "the royal family has a long history of planning coronation ceremonies.

"This will not be a snub - just a case of diary clashes."