US president Barack Obama has led tributes to Muhammad Ali after the legendary boxer died aged 74.
In a statement on behalf of himself and the First Lady, Obama said: "Muhammad Ali was The Greatest. Period. If you just asked him, he’d tell you. He’d tell you he was the double greatest; that he’d 'handcuffed lightning, thrown thunder into jail.'
"But what made The Champ the greatest – what truly separated him from everyone else – is that everyone else would tell you pretty much the same thing.
"Like everyone else on the planet, Michelle and I mourn his passing. But we’re also grateful to God for how fortunate we are to have known him, if just for a while; for how fortunate we all are that The Greatest chose to grace our time.
Obama said that he kept a constant reminder of Ali in the White House.
He said: "In my private study, just off the Oval Office, I keep a pair of his gloves on display, just under that iconic photograph of him – the young champ, just 22 years old, roaring like a lion over a fallen Sonny Liston. I was too young when it was taken to understand who he was – still Cassius Clay, already an Olympic Gold Medal winner, yet to set out on a spiritual journey that would lead him to his Muslim faith, exile him at the peak of his power, and set the stage for his return to greatness with a name as familiar to the downtrodden in the slums of Southeast Asia and the villages of Africa as it was to cheering crowds in Madison Square Garden.
The president explained how Ali had fought against the things he believed were wrong.
He continued: "'I am America,' he once declared. 'I am the part you won’t recognize. But get used to me – black, confident, cocky; my name, not yours; my religion, not yours; my goals, my own. Get used to me.'
"That’s the Ali I came to know as I came of age – not just as skilled a poet on the mic as he was a fighter in the ring, but a man who fought for what was right.
"A man who fought for us. He stood with King and Mandela; stood up when it was hard; spoke out when others wouldn’t.
"His fight outside the ring would cost him his title and his public standing. It would earn him enemies on the left and the right, make him reviled, and nearly send him to jail.
"But Ali stood his ground. And his victory helped us get used to the America we recognize today."
Ali's words and actions were on occasion controversial, which the president recognised, but added that he had gifts which outweighed this.
He continued: "He wasn’t perfect, of course. For all his magic in the ring, he could be careless with his words, and full of contradictions as his faith evolved. But his wonderful, infectious, even innocent spirit ultimately won him more fans than foes – maybe because in him, we hoped to see something of ourselves. Later, as his physical powers ebbed, he became an even more powerful force for peace and reconciliation around the world.
"We saw a man who said he was so mean he’d make medicine sick reveal a soft spot, visiting children with illness and disability around the world, telling them they, too, could become the greatest.
"We watched a hero light a torch, and fight his greatest fight of all on the world stage once again; a battle against the disease that ravaged his body, but couldn’t take the spark from his eyes.
"Muhammad Ali shook up the world. And the world is better for it. We are all better for it. Michelle and I send our deepest condolences to his family, and we pray that the greatest fighter of them all finally rests in peace."
A number of other high profile figures from the worlds of sport, politics and beyond also paid their condolences to Ali...
The three-time world heavyweight champion, who had battled Parkinson’s disease for 32 years, was admitted to hospital with a respiratory condition earlier in the week.
His family’s spokesman confirmed Ali’s death in Phoenix, Arizona, on Friday evening local time, saying his cause of death was septic shock "due to unspecified natural causes".
A family funeral will take place in Ali’s home town of Louisville, Kentucky on Thursday.
This will be followed by a public funeral procession and memorial service the next day, which will include eulogies from ex-US president Bill Clinton and comedian Billy Crystal.