One of Canada's richest and most influential men Paul Desmarais Sr. has died, his family announced Wednesday. He was 86.

The self-made billionaire transformed an ailing backwoods bus company in northern Ontario into a $271 billion global conglomerate, and was a friend to four Canadian prime ministers, as well as Nicolas Sarkozy, George H.W. Bush and Bill Clinton.

The white-haired billionaire known for his deal-making skills was a private man. He rarely gave press interviews, preferring instead to invite friends by helicopter to his private, 75-square kilometer estate in Quebec's rural Charlevoix region.

But behind the scenes he sought to shape Canada and beyond, including as the head of Montreal-based investment holding company Power Corp. from 1968 to 1996, managing a portfolio that included insurance firms London Life and Great-West Life, European cement giant Lafarge, oil company Total and wine and spirits maker Pernod Ricard.

Born in 1927 in a French-speaking enclave in Sudbury, an Ontario mining town traditionally ruled by English businessmen, he studied commerce and then law but dropped out of university to run his father's nearly bankrupt bus company.

After reviving the family business, the young Desmarais discovered leveraged buyouts and reverse takeovers, where a smaller company sells itself to a larger one and uses the money to buy the larger company's stock. His Power Corp. was originally an electric utility holding company that he bought in a reverse takeover.

He branched out into insurance and newspapers, and other sectors from Montreal to Geneva to Hong Kong.

In Europe he partnered with Albert Frere, one of Belgium's richest men.

Desmarais was also very active in public policy through his personal contacts with powerful politicians.

His support for a federalist Canada made him enemies in his adopted province of Quebec, which is currently governed by a fragile separatist government.

In 1969, he was denounced by name in a manifesto by the separatist Front de Liberation du Quebec, which bombed the Montreal Stock Exchange and kidnapped and murdered a Quebec labor minister.

"Most people assume Desmarais's public policy involvements are designed to make him richer, that he tries to control people and events to get some desired and selfish result," Michael Pitfield, a former Canadian official who later joined Power Corp., told journalist Peter Newman.

"In fact, he's an active participant, using his power base to press for what he thinks are desirable policies."

Desmarais himself told Newman that he simply shared his policy positions with people in power, and never imposed on friends.

Former Canadian prime ministers Brian Mulroney and Paul Martin both worked for Power Corp early in their business careers, and Desmarais's son Andre is married to Jean Chretien's daughter France.

In 2007, after Sarkozy was elected French president, he awarded Desmarais with the Legion d'Honneur, an order of merit established by Napoleon in 1802. At the ceremony, Sarkozy said: "If I am the president of France today, it is thanks in part to the advice of, the friendship and loyalty of Paul Desmarais."

With an estimated net worth of $4.5 billion, Desmarais was ranked by Forbes magazine as Canada's fourth richest man and 235th in the world.

He handed over day to day management of Power Corp. in 1996 to his two sons Paul Jr. and Andre but many have said he still played an active decision-making role in the firm.

He also leaves behind his wife Jacqueline and two daughters Louise and Sophie.