Brad Pitt and Angelina Jolie failed to put in a much-anticipated appearance on the red carpet at the Sports for Peace fundraiser, where attendance started at 2,500 pounds ($3,900) a head.
Sports figures including Formula One driver Lewis Hamilton, tennis star Boris Becker and boxer Wladimir Klitschko, along with British celebs such as rocker Bob Geldof attended the party and dinner at the Victoria and Albert Museum in honour of the 70-year-old boxing icon.
Becker called him "the greatest living sportsman."
"From an athlete he became a peacemaker, he became a global warrior and just a spokesperson for the right causes," Becker said. "He has had just an incredible life."
Ali was the guest of honour at the event, which was raising money for the educational Muhammad Ali Center and for research into Parkinson's disease.
Ali has battled the degenerative brain condition for almost 30 years, and makes only rare public appearances.
But British newspapers have reported the former world champion might play a role in the Olympics opening ceremony on Friday.
Maybe, said his brother, Rahaman Ali.
"There's a possibility," he said. "He makes decisions at the last minute."
Muhammad Ali won gold at the 1960 Rome Olympics when he was known as Cassius Clay. He became a divisive figure in the 1960s United States after he converted to Islam and refused to be drafted for service in the Vietnam War — for which he was stripped of his heavyweight title. He remained defiant, regained the title and became known as, simply, "The Greatest."
Geldof, the famously grouchy Irish musician and charity campaigner behind Live Aid, said Ali was the rare athlete who had made a difference in the world.
"Muhammad Ali was intensely political, and changed the whole agenda," Geldof said. "He did it with the same bravery he did in the ring."Suggest a correction