Since when has the husband of Diana, Princess of Wales been heir apparent?
Charles, Prince of Wales Charles, Prince of Wales (Charles Philip Arthur George; born 14 November 1948) is the eldest child and heir apparent of Queen Elizabeth II. Known alternatively in Cornwall as Duke of Cornwall and in Scotland as Duke of Rothesay, he is the longest-serving heir apparent in British history, having held the position since 1952. He is also the oldest person to be next in line to the throne since Sophia of Hanover (the heir presumptive to Queen Anne), who died in 1714 at the age of 83.
Prince Constantijn of the Netherlands Prince Constantijn of the Netherlands ("Constantijn Christof Frederik Aschwin"; born 11 October 1969) is the third and youngest son of the former Dutch queen, Beatrix, and her husband, Claus von Amsberg, and is the younger brother of the reigning Dutch king, Willem-Alexander. He is a member of the Dutch Royal House of Orange-Nassau and currently fourth in the line of succession to the Dutch throne.