The Coronation will be one of the biggest days in the lives of both King Charles and Queen Camilla.
But sharing the limelight at the historic event will reportedly be his grandchildren Prince George, Princess Charlotte and Prince Louis.
The youngsters have already had a taste of royal life and were prominent during the late Queen's Platinum Jubilee celebrations last year.
And for youngest Louis, who was just four at the time, he was seen sticking his tongue out at his mum the Princess of Wales and pulling a series of faces.
However, according to one royal author, Kate has a secret code phrase she uses if she feels she needs to calm her children - and it apparently works every time.
Author Tom Quinn writes in his book Gilded Youth: An Intimate History of Growing Up In The Royal Family: "When Prince Louis misbehaved at the late Queen’s Platinum Jubilee, for example, by sticking his tongue out at his mother, Kate’s reaction was praised by teams of expert commentators.
"She apparently used a secret code to calm the children, as she does on occasions — she simply says, 'Let's take a break'.
"But as a former staffer explained, the children know these few words carry far more weight than we might imagine."
It's unknown exactly what roles if any, George, Charlotte and Louis will have at their grandfather's Coronation.
It is believed they will be among the royals taking part in a procession from the Abbey - joining their parents in a carriage behind the King and Queen, who will be in the gold state coach.
But given the fact George is second-in-line to the throne, it has been reported he might get a role during the ceremony itself.
But knowing how much scrutiny this could put the nine-year-old under, it is believed that William and Kate would prefer George's role will be small.
Sunday Times royal editor Roya Nikkhah previously told True Royalty TV's The Royal Beat: "They are very keen, but if George does have an official role, it will be quite low-key.
"They are very conscious that he will return to school on the Tuesday [after the Coronation], and they do not want him to be overwhelmed by the attention. But he may play a smaller official role."
George and Charlotte attended the late Queen's funeral last September but Louis did not as he was deemed too young.
