Prince Frederik's true love

Denmark's Crown Prince Frederik's one true love was his former model fiancé, not his current wife Crown Princess Mary, a new book claims.

Former royal correspondent Trine Villemann writes in her new tome, '1015 Copenhagen K', that Frederik should have married Katja Storkholm - who he proposed to in 1995 - but Queen Margrethe refused to let the nuptials go ahead because she was Danish.

Villemann told Australia's Seven television: "In the royal Danish family there is this tradition of you get your spouse from abroad, you don't marry a Dane, but honestly, it should have been Frederik and Katja.

"What happened when he was with Katja was that he did his Navy SEAL training, and that is something he is very proud of. That only happened because Katja was there, because she was supporting him.

"Also, when he had to go and perform royal duties which he didn't like, she would go over speeches with him and suggest changes and coach him. They were a real team. He could have been a much more confident crown prince today but, because of this silly family tradition of getting your spouse from abroad, he didn't marry her."

Villemann also claims Frederik's current wife. Australian-born Mary, is finding it difficult to cope with revelations about her husband's playboy past.

She said: "Frederik has had a milky way of beautiful, intelligent, strong Danish girlfriends and he's still in touch with these girls. What you have to remember is when Frederick grew up he didn't really have a family of his own, so what happened was when he met a new girlfriend he was almost adopted into that girlfriend's family.

"He still speaks to them and he still sees them on occasions and Mary is finding that very, very difficult to deal with."

The couple - who have two children, five-month-old Isabella, and two-year-old Christian - first met in Sydney, and married in May 2004.

However, Villemann claims friends and family of the royal couple think their three-year marriage is in trouble.

She said: "Friends and family have given me a picture of the state of affairs between Frederik and Mary. There is a strain in the marriage, definitely, which mostly stems from the fact that Mary is finding it difficult to deal with Frederik's past.

"I'm not saying the marriage is really on the rocks, what I am saying that it is under strain."