He was originally listed as participant Knud Momme, but after a press release from the court it was revealed that Crown Prince Frederik will participate in the KMD Ironman Copenhagen competition tomorrow.
The Ironman competition will be 3800 meter swimming, 180 km biking and 42,195 km running.
Politiken lists that if he completes, he will be the first royal Ironman.
He will be participating as number 45. (There are live time possibilities at the website to track his, and other participants’, progress.)