King Juan Carlos and Queen Sofia marked their 50th wedding anniversary at home today with their daughters, Infanta Elena and Infanta Cristina.

Juan Carlos, then Prince of Spain, and Princess Sofia of Greece and Denmark, daughter of the Hellenic Monarchs, married in Athens on May 14, 1962. They went through Catholic and Orthodox ceremonies to appease religious and political leaders in each country.

Contrary to tradition, Juan Carlos was formally called Prince of Spain and not Prince of Asturias. That’s because by calling him the latter, dictator Francisco Franco would have legitimized Juan Carlos’ father as rightful King of Spain. Don Juan de Borbón y Battenberg was living in exile in Portugal.

The wedding, which some critics compare to a “contract,” was important for both royal houses. Greek Queen Frederica of Hanover wanted her daughter Sofia to find a prince that could make her queen someday. At the same time, Prince Juan Carlos needed someone who could help him restore Spain’s monarchy.

Historians consider the union, and Queen Frederica’s counsel, essential to helping Juan Carlos succeed General Franco as Spanish head of state. Even though Franco had been grooming the Prince for years, nobody knew if Juan Carlos would actually manage to become King.

Franco, who spied on the young couple living at the Zarzuela Palace near the Generalissimo’s own residence of El Pardo Palace, wanted to make sure Juan Carlos would continue his nationalist movement. At the same time, the world’s leaders were wary of the young prince’s commitment to Democracy. And his father in Portugal wanted to become king himself.

Spanish Television aired this mini-documentary on the wedding, which was produced in 2002 for the King and Queen’s 40th wedding anniversary.