How the role of Princess Mary's teenage son Christian is about to change dramatically – despite controversially 'putting off tasks' when he turned 18

Crown Princess Mary of Denmark's eldest son Prince Christian will take on a very prominent role when Queen Margrethe steps down, royal experts claim.

After celebrating his 18th birthday in October, the prince broke protocol by giving up his royal allowance to focus on his education – but the study break won't last long.

When Prince Frederik becomes king and queen consort on January 14, the 18-year-old's title will change to Crown Prince Christian and he may have to act as head of state while his father is out of the country.

Danish tabloid BTFie West Madsen, head of entertainment, predicts that Christian will receive a very general royal allowance as he takes on additional responsibilities.

“The Royal House has previously announced that Prince Christian would only receive an annuity later, when he turns 21, or in the event of a possible change of throne,” she said in the behind-the-scenes podcast of the Royal House.

“The change of throne is now taking place, and therefore it is logical to imagine that Prince Christian will of course also have many more obligations.”

Fie estimates that he will receive about 9 million Danish krone, which is just under 2 million Australian dollars, to cover his expenses.

“He will have a very different role than otherwise planned, and we should also expect that appanage will follow, but how much or how little he has to take on depends entirely on what the Crown Prince couple wants,” she said.

Christian will be heir to the throne and formally appointed head of state when the future King Frederick is not in Denmark.

Princess Mary as well as Frederik's brother Joachim and Princess Benedkeek can take over as head of state if Christian is too busy.

Historian and royal expert Sebastian Olden-Jørgensen from the University of Copenhagen told the Danish publication DR Margrethe's abdication will 'undeniably' ensure that Christian will receive more official duties.

After celebrating his 18th birthday in October, the prince broke protocol by giving up his royal allowance to focus on his education – but the study break won't last long

Christian became a member of the State Council when he turned 18, a role that Sebastian has now “cemented.”

'It is customary for the heir apparent to sit on the council, so it is usually just a formality. It is much more important that he was pushed to the front as a public figure on his 18th birthday,” he said.

'Now that the Crown Prince and Crown Princess are at the wheel, it is up to them how many tasks they want to give him. We have to wait and see, but it will certainly be a lot.'

Just before Christian turned 18 on October 15 last year, it was announced that he will not receive a royal grant and will instead spend time furthering his education.

Although he would have been entitled to government funding once he reached adulthood, he decided at the time not to accept payments and become a full-time royal until he was 21 years old.

A statement on the Royal Household's Instagram page said: “Prince Christian's main priority for the coming year will be the completion of the Prince's upper secondary education.”

'It has therefore been agreed with the Ministry of Foreign Affairs that support will only be sought in the Danish parliament for a law on the annual pension when the prince turns 21, or in the event of a possible change of throne, whichever occurs earlier.'

The statement ended by saying that Christian will stay away from the spotlight, but will one day appear in public again in an official capacity.

“Only after this is it expected that His Royal Highness will participate to a greater extent in official contexts,” the report said.

'However, it depends on where the prince is at this point in his training. Until then, Prince Christian will, just like today, participate only to a limited extent in official contexts.'

Although he makes many public appearances alongside his parents and siblings, Princess Isabella, 15, Prince Vincent and Princess Josephine, both 12, Christian is not yet a full-time working royal.

At the time of the announcement, Christian was in his penultimate year of school at Ordrup Gymnasium, a public school in Copenhagen.