Ms. Borrallo includes the children have a strict 7pm bedtime every night, which has been outlined by author Louise Heren.
One of the biggest rules is introducing news foods into the children's diet, as "you don't have a fussy eater if you have a Norland Nanny."
"It doesn’t have to be strict. Just because Norland Nannies wear the brown uniform, they look quite old-fashioned, that doesn’t mean their message is old-fashioned. It’s no nonsense," Heren continued.
Some ways the nannies keep things organised is by relying on sticker charts, depending on the child, to mark particular misbehaviour.
The young royals also have limited screen time on their iPad, which is set by their parents.
Another one of Ms. Barrallo main duties is preparing the kids for royal events, including how they should behave during it.
Ms. Heren said: "She’ll say: 'This is your opportunity to show Mummy and Daddy just how wonderful you are, and you are to smile and be really good for them and then we can go inside and play.'
"Maria will know their schedule. She will be doing a lot of explaining to them what is happening.
"If the children have travelled on royal engagements, it will be jolly difficult getting the kids to bed because of the excitement and the timetable of events.
"When you see William and Kate go off to a function and the children aren’t with them, they will be having naptime."
It's quite the task! But she is very close with the family, and is considered part of it, with her close relationship to Catherine.
"I imagine she’s quite chummy with Catherine.
"When you see pictures of Catherine with the three children, she’s very hands-on, and yet you don’t have a nanny if you are doing it all yourself.
"So that partnership between them – partnership rather than member of staff – will be the case there."