Princess Anne is celebrating a special birthday on Aug. 15 because she's turning 70, and her children, Zara Tindall and Peter Phillips, gave in to an interview to reveal their mother's best and worst qualities. 

Zara said in the documentary, Princess Anne: The Princess Royal at 70, that her mother has three great qualities. She is "professional, caring and honest." Her older brother, Peter, summed up the best thing about their mother in just one word. He said that Princess Anne is "tenacious."  

Prior to the documentary interview, the siblings admitted that they debated on the best words to describe their mom. Zara insisted that it's hard to sum up Princess Anne because she is so many things. 

But the brother and sister agree that their mother can be very annoying because she never forgets anything. Zara said that Princess Anne is like a sponge who absorbs what she reads and then points out these things in conversations later on. She retains information quite well and can masterfully remember details about the charities and organizations she has helped all these years.  

It's no wonder then that Princess Anne is one of the hardest working royals, averaging at least 500 royal engagements every year. The Queen's daughter said that she has actually slowed down in recent years but she's still the royal with the greatest number of engagements.

Zara and Peter also shared that their mother loves to spend time with their children. The siblings each have two daughters – Savannah, 9, and Isla, 8, for Peter and Autumn, and Mia, 6, and Lena, 2, for Zara and Mike. It's been a family ritual for the girls to stay at Princess Anne's Gatcombe Park estate after their Sunday lunches, while their parents take a break. 

When the COVID-19 lockdown eased, their daughters spent time riding horses with Princess Anne. However, the Princess Royal apparently refused to help Zara and Peter with the children's home-schooling or outdoor learning during the school shutdown. 

Princess Anne is not going to have a majestic party for her 70th birthday because of the coronavirus restrictions. However, Queen Elizabeth treated her to lunch at Frogmore House in the Berkshire Estate before she left for Balmoral. 

According to reports, no other royal family was present for Princess Anne's birthday treat. The royal mother and daughter had a handful of staff serving and looking after them. It was a quiet celebration that was fitting of the no-fuss Princess Royal.