Communication is key for the Princess of Wales when it comes to parenting her three children. And she reportedly has a special phrase she uses if Prince George, Princess Charlotte, or Prince Louis start to misbehave in public.

Royal expert Tom Quinn revealed details of Princess Kate’s special ‘code’ in his book Gilded Youth, An Intimate History of Growing Up in the Royal Family. He wrote: “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 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.”

Similarly, when Kate is at home with her children, she will employ special methods to keep things calm in Adelaide Cottage. When one of the young royals is struggling with emotions or loses their temper, Kate and William will take them away for a ‘sofa chat’. The idea is that instead of them having alone time with their thoughts and feelings, a parent is there to help them understand what has unfolded.

Another rule employed by the couple is ‘no shouting’. Children who raise their voice are removed from the situation – and similarly, William and Kate never shout at the trio when they are telling them off. An insider previously told the Sun that Kate is “slightly stricter” than Prince William, adding that the royal couple’s nanny, Maria Teresa Turrion Borrallo, makes all decisions in agreement with the couple.

The source said: “Maria is firm but she never acts unilaterally with the children on discipline. Kate and William, along with Maria, are strict with the children but have this magic ability to appear not to be. “It is a military operation but you would never guess it because they work ferociously hard on their children’s upbringing and making it seem relaxed and happy for the three of them. They are very good at listening to the children but being firm.”

Maria has served as royal nanny since 2014. Maria was born in Spain and studied at Norland College , which prides itself on being the first educational establishment to offer childcare training. Students are taught everything from child brain development and first aid to evasive driving techniques.

“The nannies are taught everything from defensive driving to security issues to how to care for a future king or queen,” royal commentator Victoria Murphy told ABC News in May 2015. “So [Borrallo] just really knows everything that you could possibly need to know about bringing up a child.”