Family, friends and international dignitaries gathered in Montreal today to mourn the death of Paul Desmarais, one of Canada's most powerful businessmen.

The commemorative service began at the Notre-Dame Basilica at 3 p.m., and lasted two hours.

 Desmarais was a mentor to several Canadian leaders, including Brian Mulroney and Jean Chrétien, both of whom attended the service.

The guest list also included former French president Nicolas Sarkozy, former U.S. secretary of state James Baker, Quebec Premier Pauline Marois and Canadian Gov. Gen. David Johnston. 

Canadian Prime Minister Stephen Harper delivered an address, and described Desmarais as a "visionary" and a man who was proud to be Canadian.

"Canada was Desmarais's largest passion ... He was an inspiration for francophones and anglophones everywhere," Harper said.

"He saw opportunity in Canada beyond our borders."

The self-made billionaire died in October surrounded by family at Domaine Laforest, the family's sprawling estate in Quebec's Charlevoix region.

He was 86. 

Desmarais, whose political and business connections reached across Canada and overseas, started out with his family's bus firm in Sudbury.

He went on to build international conglomerate Power Corp. and gain an estimated personal net worth of around $4.4 billion.

Emotional tributes

Former prime minister Brian Mulroney was emotional as he spoke to the guests who filled the pews in the basilica.

"Every day with Paul was a good one," Mulroney said in his tribute, adding that he once told Desmarais he would throw a party for him when he turned 100 in 2027.

"He said it was the dumbest idea he'd ever heard," Mulroney recalled.

"He was a friend for all seasons ... Goodbye my Paul, and thank you."

"Desmarais was a giant. Bravo, Paul, for your exceptional work," said former prime minister Jean Chrétien.

Nicolas Sarkozy, the former president of France, was a close friend of Desmarais.

He also spoke at the service, with tears in his eyes.

"I loved this man. I can't find the perfect word to express my feelings," Sarkozy said.

"You are not gone. We did not forget you. You see Paul, I always told you: we love you, and we admire you — forever."