There was a rule. It was unspoken, as most royal rules are, but understood by everyone involved — at formal royal engagements, members of the family do not crouch down to speak to children. You stand. You maintain the distance and the posture that the occasion requires. You do not get on their level.
Diana ignored it every single time.
At hospital visits, at charity events, at school engagements — wherever there were children, Diana crouched down, sat on the floor if she had to, and spoke to them face to face. Not above them. With them. Eye to eye, at their height, in the way that any adult does when they actually want a child to feel comfortable rather than impressed.
It sounds like a small thing. In the context of royal protocol it was not a small thing at all.
The palace could not officially acknowledge it because doing so would mean acknowledging that the rule existed — and drawing attention to a rule that Diana was visibly, repeatedly, publicly breaking would have raised uncomfortable questions about why the rule existed in the first place.
So nothing was ever said. Diana kept doing it. The photographs kept showing exactly who she was.
Those images — Diana on the floor at a children's hospital, Diana crouching beside a child at a charity visit — became some of the most iconic of her public life. Not because they were staged. Because they were not.
She broke the rule every time. She never once apologized for it.