His new stepmother, a beautiful and haughty woman, unpopular and scorned by the Danish people, was a great contrast to Valdemar's mother Dagmar.

At a meeting of the Danish magnates, which King Valdemar arranged at Samsø in 1215, everyone agreed to swear an oath to Valdemar the Young, and shortly after he was elected co-king of Denmark at Viborg landsting, a practice originally practised by the French Capetian dynasty and later in many of European monarchies.

During a great feast in Schleswig in the summer of 1218, with 15 bishops and 3 dukes present, Valdemar was anointed and crowned junior King of Denmark.

He took part with his father in the unlucky hunt on the island of Lyø in 1223, where both kings were taken prisoner by Henry I, Count of Schwerin and Valdemar was imprisoned until the Easter of 1226.

[2] Count Henry demanded that Denmark surrender the land conquered in Holstein 20 years ago and become a vassal of the Holy Roman Emperor for father and son to be released.

To secure their releases Valdemar II had to acknowledge the break away territories in Germany, pay 44,000 silver marks, sign a promise not to seek revenge on Count Henry and send his son Erik to prison instead.