Constantine, the former and final monarch of Greece, who won an Olympic gold medal before becoming embroiled in his country's tumultuous politics in the 1960s and spending decades in exile, has passed away. He was 82.

Doctors at the private Hygeia Hospital in Athens confirmed to The Associated Press that Constantine died Tuesday night following treatment in the intensive care unit but had no further information until the release of an official statement.

When he ascended to the throne as Constantine II at 23 in 1964 as Constantine II, he had already garnered fame as an Olympic gold medallist in sailing. The following year, his participation in the plots that brought down the elected Center Union government of Prime Minister George Papandreou cost him much of his popularity.

Several parliamentarians' departure from the ruling party, still commonly known in Greece as the "apostasy," destabilized the constitutional system in 1967 and precipitated a military takeover. Constantine was eventually pushed into exile after clashing with the army leadership.

The dictatorship dissolved the monarchy in 1973, and a referendum held following the restoration of democracy in 1974 crushed Constantine's aspirations of ever regaining the throne.

In his twilight years, when opposition to his presence no longer served as a symbol of vigilant republicanism, he was free to return to his native country, where he had only made fleeting visits in the decades that followed, each of which caused a political and media uproar. Constantine became a generally uncontroversial individual with little affection for the Greek monarchy.

Constantine was born in Athens on June 2, 1940, to Prince Paul, the younger brother of King George II and heir apparent, and princess Frederica of Hanover. His older sister Sophia is married to former Spanish King Juan Carlos I. The late Duke of Edinburgh and husband of Queen Elizabeth II, born in Greece, was an uncle.

The family, which ruled Greece from 1863 until a 12-year republican period between 1922 and 1935, was descended from Prince Christian, afterward Christian IX of Denmark, of the House of Schleswig-Holstein-Sonderburg-Glücksburg.

Before Constantine's first birthday, the royal family was forced to escape Greece due to the German invasion of World War II, relocating to Egypt, South Africa, and then back to Egypt. Following a contentious referendum, King George II returned to Greece in 1946 but died a few months later, making Constantine King Paul I's heir.

As preparation for his future job, Constantine was schooled at a residential school before attending three military schools and Athens Law School. He also competed in sailing and karate, holding a black belt.

At the 1960 Rome Olympics, he and two other Greek sailors won a gold medal in the Dragon Class, which is no longer an Olympic class. In 1974, when he was still a prince, Constantine was made a lifelong honorary member of the International Olympic Committee.

On March 6, 1964, King Paul I died of cancer and was succeeded by Constantine, weeks after the Center Union party defeated the conservatives with 53% of the vote.

Initially, George Papandreou and Constantine had a very tight relationship, but it soon deteriorated due to Constantine's insistence that control of the armed forces belonged to the monarch.

Papandreou desired control of the ministry of defense and eventually asked to be made defense minister, as many officers were considering a dictatorship. Any non-conservative government was viewed as weak against communism. In July 1965, Papandreou resigned following an angry correspondence with Constantine.

Constantine's insistence on establishing a cabinet composed of centrist defectors, which obtained a slim parliamentary majority on the third attempt, was highly unpopular. Many believed that he was influenced by his manipulative mother, Queen Frederica.

"The people don't want you; take your mother and leave!" became the rallying cry of the tumultuous summer of 1965 Greek protests.

In the end, Constantine reached a truce with Papandreou and, with his approval, established a technocrat-led government and then a conservative-led government to hold elections in May 1967.

With the polls broadly supporting the Center Union and Andreas Papandreou's popularity rising, Constantine and his courtiers feared retribution and planned a coup with the assistance of high-ranking officers.

On April 21, 1967, a group of lower-ranking officers led by colonels, who had been informed of Constantine's plans by an informant, established a dictatorship.

The official photograph of the new government displayed Constantine's views toward the new rulers. He feigned to agree with them while preparing a countercoup with the assistance of loyal troops in northern Greece and the navy.

Constantine and his family traveled to the northern city of Kavala on December 13, 1967, to advance on Thessaloniki and establish a government there. The poorly handled and infiltrated countercoup failed, and Constantine was forced to flee to Rome the next day. Never again would he reign as king.

After a failed Navy countercoup in May 1973, the junta named a regent and abolished the monarchy on June 1, 1973. A July referendum, primarily regarded as manipulated, confirmed the result.

Constantine was eager to return to Greece after the regime toppled in July 1974. Still, experienced politician Constantine Karamanlis, who had returned from exile to lead a civilian administration, warned against it. Karamanlis, who also served as prime minister from 1955 to 1963, was a conservative, but he clashed with the court over what he saw as its excessive meddling in politics.

In 1974, following his electoral victory in November, Karamanlis asked for a referendum on the monarchy. Constantine was not permitted to campaign in the country, but the result was clear and widely accepted: 69.2% of voters supported a republic.

Soon after, Karamanlis remarked that the nation had eliminated a cancerous tumor. The day after the referendum, Constantine stated that "national unity must take precedence... I fervently hope that future events will validate the outcome of yesterday's vote."

Despite acknowledging that Greece was now a republic, Constantine continued to refer to himself as King of Greece and his children as princes and princesses until his death, even though Greece no longer recognized titles of nobility.

The majority of his exile years were spent in the London suburb of Hampstead Garden Suburb, where he was claimed to have been particularly close to his second cousin Charles, the Prince of Wales and current King Charles III.

While it took Constantine 14 years to return to his nation for the limited purpose of burying his mother, Queen Frederica, in 1981, he has increased his travels since then and has resided there since 2010. Disputes persisted: in 1994, the then-socialist government deprived him of his nationality and confiscated the royal family's remaining property. In 2002, the European Court of Human Rights awarded Constantine 12 million euros, a portion of the 500 million he had requested.

His descendants include his wife, the former Princess Anne-Marie of Denmark, the youngest sister of Queen Margrethe II; five children, Alexia, Pavlos, Nikolaos, Theodora, and Philippos; and nine grandchildren.