A statement by the family announced the death but gave no additional details. Mr. Hinduja had been out of the public eye for years because of health conditions related to dementia.

Under Mr. Hinduja, the eldest of four brothers, the Hinduja Group operated as a tightly run family network without outside shareholders or extensive public disclosures of its business portfolio, estimated at more than $15 billion. The group’s wealth and influence, however, was evident by the high-profile connections forged by Mr. Hinduja and his family.

Before moving to Britain in the 1970s, Mr. Hinduja, widely known as S.P., built ties with the shah of Iran, Mohammad Reza Pahlavi, with businesses that included dubbing Bollywood films into Farsi. In the United States, Mr. Hinduja hired advisers such as Ted Sorensen, the former speechwriter of President John F. Kennedy.

He built alliances in Britain with prime ministers, ambassadors and commercial envoys. He also was invited occasionally to banquets hosted by Queen Elizabeth II as a neighborly gesture. (Mr. Hinduja, a vegetarian, brought his own food made to his strict specifications.) He made his few public appearances at events intended to burnish his philanthropic credentials: scholarships, building a Hindu temple in England and the opening in 1999 of the Hinduja Group-funded “Spirit Zone” at the Millennium Dome in Greenwich.

“The word ‘mysterious’ always seems to go with the Hinduja name,” Mr. Hinduja told Britain’s Daily Express in 1999. “Why? Because we are a private company. We don’t need a high profile.”

Yet Mr. Hinduja’s carefully groomed public image was at times shattered by investigations into alleged influence peddling. Mr. Hinduja and his brothers were under scrutiny by Indian authorities after reports claiming bribes were paid in connection with a $1.3 billion sale of weapons by the Swedish arms maker Bofors in 1986. The Hinduja family was cleared of any wrongdoing in 2005 by a court in New Delhi.

Mr. Hinduja was also at the center of a political tempest in Britain over his request for citizenship. A Cabinet member, Peter Mandelson, resigned in 2001 after disclosures that he had phoned the top immigration official in 1998 regarding Mr. Hinduja’s application. Mandelson’s critics contended that he was doing a political favor after Mr. Hinduja’s pledge to help with the Millennium Dome.

An independent inquiry found no evidence on improper acts by Mandelson or others. Mr. Hinduja, who received his passport in March 1999, threw a lavish party that November with his family for the Hindu festival Diwali. On the guest list was British Prime Minister Tony Blair and his wife, Cherie.

The Hinduja family topped the British “rich list” in 2022 with an estimated wealth of 28.4 billion pounds, or about $35 billion. That total, compiled by the Sunday Times, included the value of British property holdings. Their biggest trophy is the family’s London hub, 13-16 Carlton House Terrace, four connected 18th century townhouses on a site that was once home to King George IV before he ascended to the throne in 1820.

The Forbes List most recently placed the value of the Hinduja family business network at about $15.2 billion, which includes health care, energy and banking in Switzerland and India. Among its flagship acquisitions in the United States was the 1984 purchase of part of the former Gulf Oil conglomerate from Chevron, and a 2012 deal for Houghton International, a maker of metalworking fluids and other chemicals.

In 1987, Mr. Hinduja led efforts to take control of Ashok Leyland, which included remnants of the defunct British automaker British Leyland.

The family had long proclaimed that its fortune was shared equally by all. “There is no ‘this is mine, this is yours,’” Mr. Hinduja said in 1996. “We have kept one kitty.”

That professed unity was torn apart as Mr. Hinduja’s health failed. His three brothers filed a legal challenge to Mr. Hinduja’s claim of sole ownership of S.P. Hinduja Banque Privée, based in Geneva. The suit cites a 2014 letter, signed by Mr. Hinduja and his brothers, reaffirming the family mantra of joint ownership of all assets.

Mr. Hinduja’s daughter, Vinoo Hinduja, countered that the letter had no legal authority. In a statement, the three brothers — Gopichand, Prakash and Ashok — said they intended to fight for shared ownership, which they called “dearly held family values.”

Srichand Parmanand Hinduja was born Nov. 28, 1935, in Karachi in what is now Pakistan but then was part of the British-ruled subcontinent. His father had started with a shop in Mumbai selling jute and textiles and later expanded to Iran, trading in food, spices and other commodities from India.

Mr. Hinduja studied in Mumbai, completing his degree at R.D. National College in 1952, after the end of British rule and the 1947 partition that created Pakistan and post-colonial India. “I have experienced the loss of my homeland,” he said.

He joined his father’s business in Iran, helping gain the sole license to import Bollywood films and dub them into Farsi. Shortly after their father’s death in 1971, Mr. Hinduja and his brothers earned the admiration of Iran’s shah by arranging convoys carrying potatoes and onions during a food shortage. Pakistan did not allow Indian drivers to enter. The Hinduja brothers recruited South Koreans and others to drive the trucks.

Mr. Hinduja and his brothers “had acquired a reputation for getting difficult things done and finding solutions where others scratched their heads,” wrote Dean Nelson, a former British foreign correspondent, in his 2017 book, “Jugaad Yatra: Exploring the Indian Art of Problem Solving.”

Mr. Hinduja moved to Britain amid the 1979 Islamic revolution that toppled the shah.

Mr. Hinduja’s wife, Madhu Srichand Hinduja, died in January. In addition to his three brothers, survivors include daughters Vinoo and Shanu. His son, Dharam, died in 1992 after setting himself on fire in a rented room in Mauritius, where he was staying with his wife. British media reported that he eloped with Ninotchka Sargon, an Australian, after the family had arranged another marriage. Sargon was doused with lighter fluid by her husband but managed to escape, police reports said.

Mr. Hinduja never publicly discussed the apparent rifts with his son over the marriage. “But to suffer makes you strong,” he said in 1999 in a rare comment on the death. “It reminds you of what life can do.”