Tonga’s King Taufa’ahau Tupou IV, a towering figure in the tiny Pacific Island nation for four decades died Sunday at 88, ending one of the world’s longest reigns by a monarch in modern times.

His death in a New Zealand hospital, after a lengthy but unspecified illness, plunged the country into a traditional mourning period.

The end of Tupou IV’s reign is likely to fuel a push for more democracy in the near-feudal kingdom, where the royal family has ruled with absolute power since tribal groups on more than 170 Polynesian islands united into a single kingdom in 1845. In recent years, his reign was marred by protests and allegations of corruption.

Tupou IV ascended the throne in 1967 after his mother Queen Salote died in 1965 and an extended mourning period. Another long grieving period is expected this time, when villagers traditionally wear black and grass-weave mats wrapped around their waists.

Before his death, Tupou IV’s 41-year reign made him one of world’s longest-serving sovereigns, after Thailand’s King Bhumibol Adulyadej, Britain’s Queen Elizabeth II and Samoa’s King Malietoa Tanumafili II.

At age 14, the future king was one of Tonga’s top athletes; he could pole vault over 10 feet, played tennis, cricket, and rugby, and also rowed competitively in a racing skiff.

But like many of his countrymen he became obese, and remained so for most of his adult life.

In the 1990s, Tupou IV led his 108,000 people on a diet and exercise regime aimed at cutting the levels of fat in a nation where coconut flesh and fatty mutton are dietary staples.

From a weight listed in the Guinness Book of Records as the heaviest for any monarch, 209.5 kilograms (462 pounds), the king shed around 70 kilograms (154 pounds) to top the scales at about 130 kilograms (286 pounds).

In recent years, traditional esteem for the monarchy waned as the royal family, which controls most state assets, appeared to be enriching itself through corrupt deals. Thousands rallied last year calling for constitutional reform to curb the royals’ power.

Under the 150-year-old Tongan Constitution the king appoints the government and most lawmakers.

Businesses and scams the late king and his children were involved with in recent years included taking ownership of the privatized monopoly Tongan power and telecommunications companies, satellite communications systems and “.to” Internet domain.

The king authorized taxpayer money to be used to start Royal Tongan Airlines, which failed. He was also implicated in Tonga giving a self-styled court jester and con man more than US$60 million to invest in U.S. death “futures” only to lose it all.

The first Tongan to graduate from a university, he won Bachelor of Arts and Bachelor of Laws degrees from the University of Sydney, Australia.

In 1947 he married Halaevalu Mata’aho, the daughter of a high chief, in an unprecedented double wedding with his younger brother, Prince Tu’ipelehake, who married Melenaite Vaikune, niece of the Speaker of Tonga’s Parliament. The king’s brother and his wife were killed earlier this year in a car crash in California.

He was crowned Tupou IV on his birthday, July 4, 1967, in the palace’s Royal Chapel in the capital Nuku’alofa in an elaborate ceremony wearing British-style regalia. The Duke and Duchess of Kent represented Britain’s Queen Elizabeth II.

Tupou IV took the throne intent on the rapid and radical modernization of the kingdom, refusing to accept that Tonga’s isolation and acute lack of resources meant it must remain a coconut- and banana-dependent backwater.

He launched plans for expanding technical education, improving land use and establishing new industries.

As the years went by his schemes became bolder and more varied, but increasingly impractical. Most failed.

There are 26 heirs to the Tongan throne directly descended from Salote. Crown Prince Tupouto’a, 57, is expected to be named the new king.