It is one of the great "what if?" stories in sport.
As part of the debate, you could ask, what if Enery's 'Ammer had landed earlier in the fourth round, giving him more time to follow up? And, what if Cassius Clay had left his chin in the path of the same left hook in a different part of the ring, without the ropes to cushion his fall?
Sir Henry Cooper, later in life, wondered aloud about that June night at Wembley Stadium in 1963.
In Clay's next fight, he would dethrone Sonny Liston to lift the world heavyweight title and soon change his name to Muhammad Ali. Cooper came close to re-routing the course of sporting history. But how close?
Eight years later, in the so-called Fight of the Century, Ali was decked by Joe Frazier in similar style, by a similar punch, in a similar part of the ring - without the ropes for support - after barely 30 seconds of the 15th and final round. Although he was to lose, Ali got up and survived to hear the final bell.
Such recuperative powers made up one of Ali's prime assets. And, even if he had lost to Cooper at Wembley, it is hard to ignore the view that somehow, somewhere, he would have resurfaced. Greatness is not easily suppressed.
And there is another "what if?" attached to Cooper's career. For his last fight, a disputed points reverse against Joe Bugner in 1971, Cooper weighed only 13st 7lbs. So, what if the cruiserweight division had been in place in his heyday?
Many believe Cooper would have been a world champion, finding a natural home in the division that now nestles between light-heavyweight and heavyweight.
The counter-argument is equally strong. As well as the two defeats against Ali (he lost the 1966 rematch at Highbury in six rounds, again on cuts), Cooper was also beaten by Floyd Patterson, Ingemar Johansson and Zora Folley - men who won or challenged for the world heavyweight title.
Patterson, Johansson and Folley could all have fought at cruiserweight also, at a time when there were fewer versions of the world title to go round.
There is a tendency at times like these, in remembering a fallen fighting hero, to wrap belts around his waist in a bout of revisionist history. Cooper, ultimately, was just short of the top drawer.
And his failings in the highest company meant he was compelled to lower his sights, indirectly creating the chances for him to become the only man to win three Lonsdale belts outright, the reward for a series of defences of the British title.
He was better than many, not as gifted as some. In the parlance of his native south-east London, he was a good 'un.