When Muhammad Ali lit the Olympic cauldron to signal the start of the 1996 Games in Atlanta, it was a startlingly emotional moment for sports fans across the world.

Ali's appearance had been kept a secret from the public, and when his image flashed up onto the big screen inside the stadium, the crowd gasped.

An estimated 3.5 billion people watched on television as Ali took the torch from American swimmer Janet Evans and climbed the stadium steps.

At the top, Ali steadied his hands, slowly raised his arm and sent the Olympic cauldron up in flames: Ali was in the spotlight once again.

I ain't got no quarrel with the Viet Cong Muhammad Ali

Tears were shed by many. Ali looked as moved as anyone, his usually impassive face breaking slightly as the roar of the crowd swept over him.

Thirty years earlier, large parts of the American public had felt far more ambivalent about Ali.

His popularity plummeted when he joined the Nation of Islam in 1964, while his refusal to be drafted for the war in Vietnam in 1967 brought down the wrath of the conservative public and press.

What many forget is that the feeling was mutual: as much as white, middle-class America hated Ali, Ali hated the country he lived in.

When he threw his Olympic gold medal into the Ohio River in 1960 after being refused service in a whites-only restaurant, the politicising of Ali had begun.

Civil rights

Away from the ring, Ali became a powerful symbol of the civil rights movement and black consciousness.

"I ain't got no quarrel with the Viet Cong", Ali had said in 1966.

Over the course of the next decade, Ali's heroics in the ring and his natural charisma found him a place in the hearts of Americans of all creeds and colours.

Cynics have suggested that white America only fully accepted Ali once he had succumbed to Parkinson's disease, rendering him unthreatening and vulnerable.

But that would be underestimating the power of his deeds and the influence of his words.