Royal expert Tom Quinn said 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 this mother, Kate’s reaction was praised by a team 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 also said the family live by a set of household rules at their home Adelaide Cottage in Windsor – including one that must be adhered to at all times. And according to a source, this rule is one they are strict on following – there is to be no shouting in the house. An insider told the Sun: “Shouting is absolutely ‘off limits’ for the children and any hint of shouting at each other is dealt with by removal.”

But rather than be sent off to their bedrooms or to the naughty step when they act up, the royal couple have a different technique – the sofa chat. The source added: “The naughty child is taken away from the scene of the row or disruption and talked to calmly by either Kate or William. Things are explained and consequences outlined and they never shout at them.”