Royal children often got a "clip round the ear" before balcony appearances.
Princess Anne's offspring Peter Phillips and Zara Tindall revealed that they were under strict instructions to behave whenever there was a big royal public gathering and Peter joked about the warnings they were given.
Zara said: "For me and like... family occasions were all about hanging out with our cousins and just having as much fun as possible."
And Peter added: "You then get a clip round the ear and say right, behave yourself, you know, we're going out on the balcony. Don't pick your nose and you know, don't yawn."
Anne: The Princess Royal at 70, on ITV at 9pm on Wednesday, July 29.
Peter, 42, and Zara, 39, are the Queen's oldest grandchildren, but their parents, Princess Anne and Captain Mark Phillips, decided not to give them royal titles.
Peter reflected on upcoming documentary 'Anne: The Princess Royal at 70': "We were always brought up on the understanding that we were gonna have to go to work. We were gonna have to go out and earn our, earn our living. Regardless of the fact of who our grandmother was or who are mother was."
Zara added: "I think it made us fight harder as well, to try and be as successful as we could be. Erm, so I definitely, you know I'm very, we're very grateful to her not giving us a title anyway."
Anne previously admitted she felt having a title was a "mixed blessing" and understood the benefits of her children not having them.
She said: "I think even then it was easy to see that it was a very mixed blessing to have a title,"
'Anne: The Princess Royal at 70' airs on ITV at 9pm on Wednesday, July 29.