He had had Alzheimer's disease for several years, his son Michael said in announcing the death.

Make that Prince Michael.

Members of the Bates family still claim dynastic dominion over what they call the Principality of Sealand, a rudimentary platform of concrete and steel rising out of the water seven miles southeast of the main British island. And they are looking to expand the royal family.

Even if you never get the chance to visit — the trip requires a helicopter ride or a willingness to be hoisted by crane from a boat — you, too, can join the royal court of one of the world's most enduring and entrepreneurial micronations.

The official Sealand Web site sells titles (the "Count/Countess Title Pack": about $320), identity cards, stamps, wristbands and e-mail addresses (just under $10 for six months).

"It helps pay for the whole Sealand thing," Michael Bates said.

A country does need an economy, and the effort to sustain Sealand with Internet commerce is at least somewhat consistent with why Roy Bates arrived there in the first place.

In the 1960s, Mr. Bates, a former major in the British Army, was among a group of disc jockeys who tried to avoid England's restrictive broadcasting regulations by setting up pirate radio stations on some of the country's abandoned offshore outposts, which had been used to fire ground artillery at German aircraft during World War II. Mr. Bates began broadcasting from one outpost within the three-mile limit of England's territorial waters, and when he was driven from there in 1966 he planned to start a station at Her Majesty's Fort Roughs, which was in international waters. Instead, he founded Sealand.

On Sept. 2, 1967, Mr. Bates declared it an independent nation, himself its royal overseer and his wife, Joan, its princess. It was her birthday.

"They had a huge love affair," Michael Bates said. "He really worshiped her."

Mr. Bates was emboldened the next year when, after he faced weapons charges for firing warning shots at an approaching British vessel, a British court ruled that it had no jurisdiction over the case because the incident had occurred in international waters.

A decade later, a greater drama ensued when a group of Germans with plans to build a luxury casino on the platform tried to take control of Sealand while Mr. Bates and his wife were away. They held Michael Bates hostage for several days before Roy Bates stormed Sealand and retook it in a dramatic helicopter raid. He imprisoned one of the men there. When the German government sought Britain's help in freeing him, Britain declined to intervene, citing the 1968 ruling.

Germany sent a diplomat, the man was eventually freed, and Mr. Bates asserted that Germany had effectively recognized Sealand as a sovereign nation.

Even after Britain expanded its territorial waters to 12 miles from shore, it mostly left Sealand and the Bateses alone. The family has explored various means of economic development, including housing an Internet company that wanted to create a financial haven without government oversight. It is still considering playing host to an online casino. WikiLeaks is said to have considered moving its servers there.

For now, most of Sealand's trade is driven by Roy Bates's grandson James — Prince Royal James — who oversees the Sealand Web site.

"The history of Sealand is a story of a struggle for liberty," the Web site says. "Sealand was founded on the principle that any group of people dissatisfied with the oppressive laws and restrictions of existing nation-states may declare independence in any place not claimed to be under the jurisdiction of another sovereign entity."

Paddy Roy Bates was born on Aug. 29, 1921, in London. His father served in the Royal Artillery in World War I and suffered lung damage from being gassed. The family moved to Essex with the goal of improving his health. According to an account on the Sealand Web site, Roy Bates was the only one of five siblings who survived childhood, and he barely survived his 20s, suffering several war wounds as a British soldier.

"He once said that despite the paradox of him breaking away from the U.K. with Sealand, he would do it all again if his mother country needed him," the account said.

Besides his son, his wife and his grandson, Mr. Bates's survivors include a daughter, Penelope Hawker, who has not been especially involved with Sealand, and a granddaughter.

Roy Bates was not just a self-made prince, he was a self-made man. After the war, he imported beef and ran butcher shops. He built fishing boats in Essex, and some family members still fish commercially for cockles, mussels, oysters and other seafood. None of the Bateses live on Sealand, though they do visit and provide upkeep. A caretaker usually occupies the place, which includes modest living quarters, a kitchen, a chapel and an exercise area. Sealand was abandoned briefly after a fire in 2006 but later repaired.

Michael Bates has said in recent years that the family would consider selling the place — or, given the complications of selling a supposedly sovereign nation, leasing it — but he said on Thursday that no sale was planned. He expects his descendants to preside over Sealand for many generations to come.

"The family," he said, "plans to continue the legacy."