Ah I see. How do we know there were no sub-four minute miles before this. Well, we don't. Perhaps Bannister's record should be known as the first officially timed sub-four.
The world is divided into positive believers and negative non-believers.
Those who watched and watch again that 'magic' moment in Oxford, 58 years ago will always accept and believe that it was indeed the first sub-four minute mile. They are positive believers.
Proving that negative non-believers do not matter.