Like a bolt from the blue, Cassius Clay - soon to be Muhammad Ali - shocked the world on 25 February, 1964.
Lithe, quick and bold as brass, the rank outsider stopped feared heavyweight champion Sonny Liston after six rounds.
That win is fondly remembered as the start of a special sporting career, but few gave Ali a chance on fight night in Miami.
Liston was a terrifying individual, widely regarded as boxing's biggest bully since Jack Johnson, the first black heavyweight world champion.
Ali, barely more than a boy at 22, looked frail by comparison and relied on his larger-than-life attitude.
He already called himself 'The Greatest' and was so merciless in his taunting of Liston that some sincerely thought he had signed his own death warrant.
'The Louisville Lip' even had the audacity to roll up outside the champ's house in a painted battle bus, before ringing on the doorbell and shouting out abuse.
But Ali's bravado could not hide his fear, which is what makes the first round in Miami one of the most significant of his life.
He left his stool wide-eyed with unfulfilled promise and returned to it convinced that his wildest boasts could actually come true.
In between times, he danced around Liston, jabbing and taunting as the champion thrashed wildly at thin air.
Ali, who later confessed his surprise at making it through the opening round alive, started to dazzle his lumbering foe with speed and guile in the following rounds.
But he faced another massive test before claiming the heavyweight crown. In the fifth, he was mysteriously blinded by a substance that many believed came from Liston's gloves.
Forced to take punches, Ali showed the durability that would characterise the second half of his boxing career, until with sight restored, he was able to attack again and eventually forced a disillusioned Liston to retire on his stool.
What followed was pure Ali theatre.
The new champion leapt around the ring shouting and screaming at the top of his voice: "I'm the champion of the world. I'm the greatest thing that ever lived. I'm so great I don't have a mark on my face.
"I shook up the world! I shook up the world!"
Ali was absolutely right.
He had shaken up the sporting world and would go on to transcend sport with his charm, quick wit and even quicker gloves in a way that no athlete had done before or since.
There would be better boxing displays in his career and he would be made to reach even deeper to prevail, but 25 February 1964 will always be one of the most significant Ali moments.
On that night, he made good on all of his youthful bragging, taking giant strides towards living up to his self-proclaimed moniker: 'The Greatest Of All Times'.