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.
Margrethe II of Denmark Margrethe II (Danish: "Margrethe 2." , ] ; Faroese: "Margreta 2." ; Greenlandic: "Margrethe II" ; full name: "Margrethe Alexandrine Þórhildur Ingrid"; born 16 April 1940) is the Queen of Denmark. She is also the supreme authority of the Church of Denmark and Commander-in-Chief of the Danish Defence. Born into the House of Glücksburg, a royal house with origins in Northern Germany, she was the eldest child of Frederick IX of Denmark and Ingrid of Sweden. She succeeded her father upon his death on 14 January 1972, having had become heir presumptive to her father in 1953, when a constitutional amendment allowed women to inherit the throne. On her accession, Margrethe became the first female monarch of Denmark since Margaret I, ruler of the Scandinavian kingdoms in 1375–1412 during the Kalmar Union. In 1967, she married Henri de Laborde de Monpezat, with whom she has two sons: Crown Prince Frederik (born 1968) and Prince Joachim (born 1969). She has been on the Danish throne for 45 years, becoming the second-longest-reigning Danish monarch after her ancestor Christian IV.