In 1972, when HRH Prince Vajiralongkorn had come of age, His Majesty formally designated him as Heir Apparent through a traditional ceremony held in the Ananta Samakhom Throne Hall, making him the third crown prince since the beginning of the Rattanakosin period after Crown Prince Maha Vajirunhis, who passed away at the tender age of 17, and Crown Prince Maha Vajiravudh, who went on to become King Rama VI.