The one rule Australian-born Crown Princess Mary keeps in place to ensure some sense of normality while living in a royal palace is there is to be no distraction at the dining table.

“We always gather around the table… whenever possible, for breakfast. And without a cellphone!” she once told a French magazine.

The soon-to-be queen of Denmark has taken a very public stance regarding the digital world’s impact on children’s mental health and bullying at school. And she has practised what she’s preached.

As a mother of four teenagers – the eldest of whom will become the heir to the throne on Sunday – she has spoken on several occasions about ensuring their privilege is balanced with her protection. And phones in particular are a bugbear.

It has been more than two decades since the Tasmania-born royal became a household name, capped off by what was then described as the wedding of the century, broadcast live on several Australian television networks.

The 51-year-old’s celebrity status has only grown abroad while in her own homeland the novelty, at times, seemed to wear off. For years, she and her family have been able to return to Australia on holidays almost unnoticed.

For much of the 20 years since marrying and starting a family, the University of Tasmania law graduate has focused on giving her children the most normal upbringing possible – circumstances considered. As they entered adolescence, she admitted, it became a tough task. Life nowadays, she said, is different from growing up in sleepy Hobart in the 1970s and 80s.

“We are more exposed,” she told Point De Vue ahead of her 50th birthday in 2022. “In this day and age, anyone can take photos or make films, anywhere. It is important that our children are aware of this. And they are.

“But adolescence is a period of transformation, during which we are more vulnerable. These are years when we learn a lot and make mistakes. I hope they continue to have the freedom and space to make these mistakes.”

Several Danish royal commentators have this week described Mary’s role in the transformation of her husband’s public profile as vital. The man who will become King Frederik X was regarded as a sometimes lost and rebellious teenager who did not want to take the throne.

He once told a journalist that his father had occasionally subjected him to gifles – French for slap – although he later denied he had ever been beaten. In the late 1980s and 90s, Frederik had a public profile not dissimilar to that of Britain’s Prince Harry.

He was visibly irked by the media attention and more comfortable partying than making speeches. In 1988, he broke his collarbone and required stitches to his head after swerving his car off the road in the south of France, falling out of the vehicle and landing in a brook.

“He has had a very difficult and unhappy upbringing, a strict one,” says royal expert Trine Villemann, whose book 1015 Copenhagen K – named after the postcode of the Danish royal palace – is widely viewed as the definitive biography of the prince’s childhood. “He was brought up by a distant mum and Frederik used to hide in the corridors if he heard his father’s voice.”

Villemann says for much of their marriage Frederik enjoyed a party and spending time with his large group of friends, while Mary was often seen to be left at home caring for their children. “She locked herself up in the royal palace and threw the key away. For a long time we hardly knew much about her,” she says.

“But Queen Margrethe is grateful to her daughter-in-law for the steady hand she has shown her son and doesn’t want to lose her. Without her, Frederik is lost.”

As a young mother, Mary was still mastering the Danish language and was subject to some sneering criticisms in the media. While she put effort into her eponymous foundation and charity events, the spotlight was, more often than not, on her husband.

But it was Mary’s speech at a gala banquet at Christiansborg Palace on May 26 in 2018 that ensured the Danes fell in love with this Australian woman all over again.

“People still talk about the speech,” says Villemann. “It was personal and it gave us an insight into her and her family life that we as Danes had never really seen.”

Speaking in her adopted tongue, Mary lifted the lid on their home life, painting her husband as a devoted father idolised by his children, while also acknowledging the complexities of his childhood and once reluctance to fulfil his destiny.

“And according to your children, you are also a very successful father,” she said. “They describe you as sweet, fun, wonderful, wise, brave, helpful, cool and handsome.

“You are their hero. They know that you believe in them [even] when they doubt themselves. You encourage them to believe in themselves. And when on the rare occasion you get cross, you quickly put it behind you, just as your father did.”

Days before the pair become king and queen, Mary had to confront rumours in a Spanish tabloid that Frederik had had an affair with a Mexican socialite.

In November, Lecturas published photographs of the prince strolling around Madrid with Genoveva Casanova. It claimed the images showed him leaving Casanova’s apartment the morning after an alleged dinner date. Casanova has denied any romantic liaison and has threatened legal action.

Apart from one cryptic social media post, Mary has remained quiet.

She has been particularly protective of her eldest son, Prince Christian, who is destined to succeeded his father but appeared reluctant to fully launch himself into royal life. Royal commentators now agree he is more confident and at ease publicly than his father ever was. Mary gets the credit for this.

After allegations of sexual abuse and bullying surfaced at Christian’s boarding school, Herlufsholm, in 2022, his parents announced the then 16-year-old would be leaving and his sister Princess Isabella would not start as planned. Christian was not connected to the allegations.

“Bullying, violence and indignities are never acceptable. We must respond to the painful and devastating incidents by insisting on changes that ensure a safe environment for all,” they said in a statement at the time. “We must recognise the courage of those who have shared their violent experiences.”

Mary once said that being royal came more naturally to her children than people expect. From a young age, the children have accompanied the couple, when appropriate, to give them an insight into their future work.

“It is essential that they are proud of who they are, of belonging to this family and of what it means to the Danes,” she said in 2022. “Prince Christian has a more defined trajectory than his brother and sisters, but it is up to him to build this destiny as best he can.”

Mary’s own 50th birthday nearly two years ago was marked on national television with a short film featuring her children. Prince Vincent, Princess Josephine, Isabella and Christian praised their mother for her ability to sing and dance.

“I think she is very good at dancing,” Vincent said. Christian added: “She is especially fond of the air guitar when rock music is played.” Isabella replied: “She is good at playing drums.”

The children also mocked their mother’s Australian accent and conceded that after 20 years she still has some expressions that sound funny in Danish – words like “apple” and “little”. But Christian said his mum had placed a big emphasis on doing her work “thoroughly”.

“It must be absolutely perfect,” he said at the time. “If she has been on a journey, she comes home and tells us what she has experienced, what she has done and where she has been. If she has been to Africa, she tells a little about the schools. How the children experience it. And it gives the four of us an insight into how well we actually have it here in Denmark”.

Isabella said she was always on hand for support. “If you have a hard time with something, or it has been a hard day at school, she is always good at just talking about it,” she said.

Mary lost her own mother when she was in her mid-20s and has said on several occasions that Henrietta remains a guiding light in her life. “Losing my mother changed my outlook on life, my way of thinking. It also helped shape me into the person I am today, with added depth,” she once said.

“If my mother looks at me, I think she won’t really need to say anything – her warm smile will speak for her better than anything.”