Crown Princess Mary and Crown Prince Frederik’s eldest son, Prince Christian, can now act as regent. Weeks after celebrating his 18th birthday, Christian participated in a meeting of the Council of State, where he made a solemn declaration that he will abide by the Constitution.

In the event that Queen Margrethe II and Crown Prince Frederik are prevented from governing, Christian can now be appointed regent. According to the Royal House, this is the first time in more than 100 years that “there are both a successor to the throne and an heir to the throne of legal age who can step in as regent.”

Both Crown Prince Frederik and Queen Margrethe attended the meeting on Tuesday, Nov. 14. It was presumably “the first time in the history of the Constitution that three generations in the line of succession” were present in the Council of State at the same time, per the royal House.

While Christian, who is second in line to the Danish throne, attended the meeting on Nov. 14, he will not have a seat in the Council of State until a succession to the throne has taken place. Portraits of Christian with his paternal grandmother and parents were released following the meeting.

Christian celebrated his 18th birthday on Oct. 15 with a gala dinner hosted by his grandmother Queen Margrethe at Christiansborg Palace. The Danish Prince called it “an absolutely unforgettable evening.”

In a speech at the celebration, Her Majesty said, “Dear Christian, your 18th birthday is an important day, with it you come of age, just as it happens for all other young Danes. But there is still a difference. Your path in life is already set, for one day you will follow your father, just as he will follow me one day. You become a link in the long historical chain that has bound our country together for centuries.”

Queen Margrethe also told Christian that his “apprenticeship only begins here, regardless of what you choose to do.” The Danish monarch said, “You have good skills, you are physically active and you are aware of your responsibilities. You have empathy, you have always shown that, not least towards your siblings. The good qualities that you possess and the ballast that you bring from home will follow you everywhere. May your 18th birthday be a good and festive prelude to many good years as you expand your horizons and develop all that lives within you.”