Five months after unexpectedly becoming the new King and Queen of Denmark, Frederik and his Australian-born wife Mary continue to celebrate their modern-day fairytale marking a milestone anniversary.

Wearing matching navy puffer vests, the Danish Royal House released a new shot of Fred, 55, and Mary, 52, smiling aboard the royal ship, Dannebrog, on their 20th wedding anniversary.

On the second leg of an extended summer tour to Scandinavia – they completed their first state visit to Sweden last week – May 14 marked two decades since the royal couple said ‘I do’ in 2004 in Copenhagen.

“The arrival to the Norwegian capital [Oslo] also happens on a very special day. It’s the King and Queen’s 20th wedding anniversary,” a statement read on their official Instagram.

It has been mostly plain sailing and a rock-solid marriage for the former Hobart resident Mary (née Mary Elizabeth Donaldson), and Fred, who share four children, Crown Prince Christian, 18 (who took his father’s former title upon the change of reign), Princess Isabella, 17, and twins Prince Vincent and Princess Josephine, 13.

Until a bump in the road in November, when Fred made headlines after being snapped by paparazzi walking through a park with art expert and socialite Genoveva Casanova during a ‘private trip’ to Madrid, Spain.

The pair then reportedly had a very public dinner together at the restaurant El Corral de la Morería in the heart of the city.

Casanova issued a strongly worded statement via her lawyers, denying all allegations of a romantic relationship with the royal.

Mary remained dignified throughout the scandal and kept a united front, culminating in an unexpected change of reign.

Within two months, then-Crown Prince Frederik was proclaimed King in January after his mother Queen Margrethe signed a declaration of her abdication on the 52nd anniversary of her accession, becoming the first Danish sovereign to voluntarily do so in nearly 900 years.

All eyes were on the next-generation royal couple as a crowd of 100,000 gathered outside the Danish parliament to celebrate their new King and Queen.

“I want to return the trust I meet,” Fred told the 100,000-strong crowd from the balcony of the Danish parliament.

“I need trust from my beloved wife, you, and that which is greater than us,” he said before drawing Mary in for a kiss.

Mary Donaldson’s transformation into a princess seemed like something straight out of a fairytale. Photo: Getty

The royal couple met at the Slip Inn in Darling Harbour in September 2000 during the Sydney Olympics.

Working as an advertising executive at the time, Mary found herself chatting to “Fred” and instantly hit it off.

The couple soon began dating long distance, and Mary said their strong communication skills helped establish a deep connection.

She moved to Europe in 2002, and taught business English in Paris before heading to Denmark to learn Danish and work as a project consultant for Microsoft Business Solutions.

“Moving to Denmark was a huge change in my life – a new culture, new language, new friends, and another way of life,” she told The Australian Women’s Weekly.

A year later, Mary and Frederik’s engagement was announced on October 8, 2003, to much fanfare.

Fred and Mary looking casual at Fredensborg Castle on May 2. Photo: Getty

Home away from home

Mary has never forgotten her Australian roots, and has often brought her children to visit friends and family Down Under.

She most recently touched down with her youngest children, 12-year-old twins Vincent and Josephine, for a private family trip in December.

For now, Mary and Fred will make Dannebrog their official residence over the northern summer, to mark “close relations between the Nordic monarchies”, according to a palace statement.

Their first state visits included meeting the sovereigns of Sweden and Norway.

In June, the couple “will sail north on a cruise of the Realm”, and will visit the Faroe Islands in mid-June, and then Greenland later that month.