King Juan Carlos of Spain signed the bill of his abdication in favor of his son, Crown Prince Felipe.
King Juan Carlos, 76, signed the bill at a ceremony in the Royal Palace in Madrid, which was attended by only 160 guests.
At midnight local time, Crown Prince Felipe, 46, will become king although the event will not be marked in public until Thursday morning.
The succession was endorsed by both of Spain’s main political parties.
Before the signing, King Juan Carlos sat with Queen Sofia to his right and Crown Prince Felipe and Princess Letizia to his left as the content of the law was read out.
After Juan Carlos had signed the document that will end his rule, PM Mariano Rajoy also signed the law. Moments later, the assembled guests applauded, the prince’s two daughters joined the royal group and the national anthem was played.
Prince Felipe will head to the lower house of the Spanish parliament on Thursday for the first royal transition the country has seen since democracy was restored after the death of General Francisco Franco in 1975.
The ceremony at 10:30 local time will take the form of a proclamation rather than a coronation, in part because of the economic hardship that many Spaniards have experienced in recent years.
Juan Carlos, who has been king for 39 years, formally brought his reign to an end in the Hall of Columns at the 18th Century royal palace, the same room in which Gen. Francisco Franco’s body lay in state in November 1975.
Father and son both wore suits which bore the insignia of the order of the golden fleece, Spanish media reported.
King Juan Carlos announced his decision to abdicate on June 2, saying that a “new generation must be at the forefront… younger people with new energies”.
Although he was for many years a popular monarch, King Juan Carlos reputation has taken a knock from a corruption investigation into the business dealings his daughter’s husband and an lavish elephant hunting trip he took to Botswana in April 2012 in the midst of Spain’s financial crisis,
As Juan Carlos was Spain’s first ruling monarch for 44 years, a new law of abdication had to be passed by both houses of parliament under the country’s 1978 constitution.
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